Monthly Archives: December 2011

Hygrophila pinnatifida now available commercially in the USA

  By robert | December 22, 2011 - 5:52 pm | Hobby News
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Florida Aquatic Nurseries, the largest commercial wholesale grower of aquatic plants in the USA, is now offering Hygrophila pinnatifida in limited supply and is available from any of their dealers and online retailers. http://www.azgardens.com/c-50-newlimited-aquarium-plants.aspx is currently selling it, and www.aquariumplants.com should be able to get it if you ask them. For the past year the plant has been sold by hobbyists for over ten dollars per stem, but commercially it will be sold per bunch of 4 or 5 stems. AZ Gardens current price is about ten dollars per bunch, (not per stem), and the price should be falling over the next few months. A few aquarium stores across the country have began selling it as well.

This is an easy to grow plant with good color and an interesting leaf texture. For more information about the plant, see

http://www.aquabotanic.com/?p=1027

 

Ludwigia inclinata ‘tornado’

  By robert | December 22, 2011 - 3:52 pm | Aquarium Plants
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By Robert Paul Hudson

A plant beginning to be circulated around the USA between hobbyists is Ludwigia inclinata ‘tornado’ which has twisted leaves growing in whorls from thick stems. It is a mutation in captivity found in Vietnam, probably from Ludwigia inclinata cuba.  It is not grown commercially in the USA. All inclinata species are a challenge to grow for the beginner, and some very challenging for even the most experienced. The cuba variety is the least complicated to grow.  Inclinata species are soft water plants and do the best in acidic water.

Cuba grows to be quite large for a stem plant and the thick stems are a telling sign. It is mostly green but gets some red coloration at the tips and the center of the whorl.  It requires bright light and lots of C02, and when its growing well it takes up quite a bit of room. This mutation seems to have many of the same characteristics according to reports from hobbyists. It is also mostly green with some hints of red.

Native L. inclinata species are native to South America and Cuba. This mutation has never been discovered in those regions. There have been some reports of the leaves losing their curl after being propagated, while others have reported that this is not the case.

The plant is rare because it is not yet being mass produced commercially, and is only being traded among hobbyists. It will be interesting to see if this changes. Ludwigia inclinata green and Ludwigia inclinata cuba are being grown commercially in Florida and are fairly easy to obtain.

Diagnosing plant problems part two- treatment

  By robert | December 20, 2011 - 7:16 pm | Aquarium Plants
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by Robert Paul Hudson

In the previous article I showed on a chart some of the signs of common nutrient deficiencies. Here we will talk more about how to correct them.

In general those nutrients that are measurable in the aquarium have ideal levels for the average tank with moderate to high light and C02:

  • Nitrates 10-20ppm
  • Phosphates 1.0-2.0 ppm
  • Iron 0.1-1.0 ppm
  • Potassium 10-20 ppm
This can vary depending on your aquariums individual needs, various plant species, lighting, and other conditions, but generally speaking these are considered the ideal levels. Potassium test kits are harder to find, but they are out there.
Other macro nutrients, calcium, magnesium, sulfur, are near impossible to measure for the hobbyist, and effective target ranges have not been established.  Trace minerals other than iron are also just as ambiguous.  Soft water plants do not need that much calcium. Hard water usually has plenty already. The easiest way to add magnesium to the water is with Epsom salt, a natural mineral salt high in magnesium and available at any drug store.
Nitrogen in the form of nitrate can be supplied by a dry or liqiud fert.  Potassium is available in chemical form as Potassium nitrate, which supplies both nitrate and potassium. There are other forms of potassium as well. Some commercial aquarium fertilizer products are available as straight nitrate, or potassium, or phosphate to enable you to dose each separately, but many products are “all in one” which may give you too much of one thing, and not enough of something else.
Here are the raw chemicals that you can buy:
  • KNO3 will dose nitrates and potassium
  • KH2PO4 will dose phosphates
  • K2SO4 will dose potassium
  • Plantex CSM+B will dose traces and iron
If you are using store bought products, the best thing is to follow the directions on the bottle and test the water. If you are buying raw chemicals it is best to read up on the subject more and take a look at the “Estimated Index” method which is also written about on this blog.

 

 

Why do my stem plants always rot away?

  By robert | December 20, 2011 - 4:04 pm | Aquarium Plants
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by Robert Paul Hudson

One of the most common questions repeated over and over again on internet forums is “why do the stems of my plants keep rotting away when my rooted plants grow without any problems?”  More often than not people dance around this question looking at C02 levels, fertilization, substrate issues, and ignore the most obvious… LIGHT.

Cut stems always rot from the bottom up never taking root in the substrate when lighting levels are in adequate for growth. ALWAYS. It is the first and most obvious sign of inadequate light.  When you increase the light level, stem plants react quickly even if other factors are limiting. Some of the most prolific growing stem plants will take root under lower light levels, and many of these are considered invasive for that reason and have been banned by our government, but in general, most stem plants need higher light levels than rooted plants which grow from a crown, tuber, or rhizome.

Lets take Ludwigia for example. The most common Ludwigia species are repens, arcuata, and palustris, all of which are native to North America, and considered easy to grow. But, they are also the first to rot away from the bottom up if light is inadequate.  Typically what happens is the leaves in the lower portion of the stems begin to fall off and leave naked stems while the upper portion that is closer to the light appears to continue to grow and produce more leaves. The portion of the stem buried in the substrate starts to get soft and turns to mush and spreads upward to the point that the stem breaks off and floats to the surface. People often then replant the stems and the same thing happens again and again and again until there is nothing left.

Now you can attempt to compensate for this by dramatically raising C02 levels, but the easiest solution is to simply increase your light level, (not the duration of the lights). The exception to this to some extent is a properly set up Walstad type of planted aquarium which can get away with much lower light levels, but even in a Walstad tank, if stems are rotting and not taking root, it is most likely a lighting issue.

“But I have T5 lights”

T5 lighting is the latest technology for higher intensity lighting, but depending on the size of your tank and the height, one T5 bulb is not going to be enough, or even two in some cases. Vaughn wrote a nice article last month about how to gauge your lighting,  but even his estimates may be considered somewhat conservative.

 

 

Ceratopteris pteridoides: floating fern

  By robert | December 20, 2011 - 3:25 am | Aquarium Plants
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Ceratopteris pteridoides

 

by Robert Paul Hudson

 

This floating fern has large leaves and a very distinctive appearance unlike any more common specie of Ceratopteris that is widely used in the hobby. What very few people realize, including one proclaimed expert aquatic plant forum, this plant known as Antler fern is native to the USA! It is found throughout Florida and Louisiana, and was not an introduced specie.  It is also native to Brazil, Ecuador, the West Indies, China, and Southeast Asia.

The leaves consist of sterile and non sterile leaves that differ sharply in appearance: the sterile leaf is usually broad basal lobes while the fertile leaf is finely disceted into long narrow ultimate segments. Transitional leaves are deeply pinnatifid.

The plant has a short fleshy stipe- (stipe def. a supporting stalk or stem like structure that supports the petiole).  The stipe in some plants is decidely swollen.

This photo shows all the leaf types that can occur on the same plant. This is the plant at its full glory! Looking at this photo you can never mistake it for another Ceratopteris specie.

Ceratopteris pteridoides typically grows in swamps and ditches and is sometimes caught in mud flats from receding water where it will root in the mud.  It can grow from partial shade to full sun and has no particular water parameter requirements. Growth is slow to moderate and it reproduces by adventitious plants. It is occasionally sold commercially as a pond plant. It is best grow in open top aquariums, and when the plant becomes to large you will probably want to discard them while keeping the plantlets.  If you have an opportunity to get this plant, grab it! It is fascinating to watch it grow to maturity.

 

 

 

 

 

Diagnosing problems with aquarium plants

  By robert | December 16, 2011 - 9:34 pm | Aquarium Plants
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Diagnosing Problems
by Robert Paul Hudson

Problem Symptom Treatment
insufficient light plants weak and frail, leaves pale, stem plants have few leaves, or more leaves on tops.  Stems rot, weak stalks on rosette plants More light! Correct light intervals, (10 to 12 hours)
Substrate problems Gas bubbles come out from the substrate when you poke it, burrowing snails aren’t burrowing, poor root systems, roots turn black and rot. Substrate is too compact, loosen and vacuum. Can be caused by heavy amounts of decaying organics deep in the substrate.
oxygen deficiency Fish are prone to disease, stressed, gulping for air at the surface. After long periods of this plants become stunted. Cause: insufficient light or nutrients, which slows down  plant growth and production of O2, breakdown of nitrogen ceases. Over fertilization of CO2. Treatment: check lights, filter, CO2 system, increase circulation, fertilize if needed
Potassium deficiency Yellowing of the margins of young leaves, iron chlorosis, yellowing and curling of older leaves Add more potassium!
Iron  chlorisis yellow leaves that become brittle: too little iron, too little potassium, also caused by very hard water add more iron!
Phosphorus deficiency Premature fall off of older leaves add an NPK fertilizer containing phosphate
excess phosphorus algae blooms, dirty water more frequent water changes, substrate cleaning, no overfeeding the fish, no over fertilization
Calcium deficiency New leaves appear damaged and die off, yellow leaf edges add more calcium!
Magnesium deficiency Yellow spots on old leaves.
Symptoms do not appear until the deficiency is well established. The plant will be stunted. Leaf veins will stay
green while the remainder of the leaf turns yellow. Brown spots will appear and the plant will dry out. Flowers will be slow to develop, if at all. Flowers that do grow will be lackluster.		 Add more magnesium!
Nitrogen deficiency Old Leaves turn yellowish.  Small stunted plants with very large root systems; leaves smaller and lighter in color than normal; slow growth.  Paleness will start at the tips of the lower leaves. If this deficiency continues, the foliage will continue to develop, but stems will be spindly, sappy and soft, flowering will be delayed, small fruit will grow and the plant will be more susceptible to disease. add more nitrate
Cryp rot a disease affecting cryptocorynes. Starts with small holes in leaves then disintegrating, and the whole plant above the root system melts away Thought to be triggered by high nitrate levels, sudden drop in temperature, or sudden environmental changes, and frequent transplants. Do regular water changes and keep environment stable. If left alone, plant will grow back after melt down.

Fontinalis antipyretica: Willow moss

  By robert | December 12, 2011 - 3:57 pm | Aquarium Plants
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by Robert Paul Hudson

Fontinalis antipyretica

 

Fontinalis is found throughout North America, Asia, and Europe. It is a true cold water plant, particularly in North America. There are several species in North America alone and two variations of Fontinalis antipyretica: the common variety and the gigantea variety. The “gigantea” has reached lengths of two meters, leaves 5-8 mm wide, and mats that cover an entire stream bed. The standard variety typically grows in fast moving streams while the gigantea version is more often found in quiet shallow pools. Typically its natural water habitat is low in pH between 4 and 5.5.

Excessive light and heat have the most dramatic effect on this plant. Studies have shown that 15 degrees C is optimum and after about five weeks of being exposed to 20 degrees C or higher it will turn from its beautiful dark green to a murky brown color and stop growing. This is when many hobbyists believe the plant is dead, but when the temperature drops back down it will usually turn back to the green color and begin growing again.

Willow moss is particularly sensitive to copper. First the tips of the branches show the signs of chlorosis at copper levels of only 3 ppm and then at 10 ppm, irreversible plasmolysis occurs and the cells are colorless. If you are trying to eradicate snails, do not use a copper based treatment with this plant in the tank.

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The most practical uses for this plant in the aquarium would be for fish breeding, black water tanks, North American native species tanks, goldfish, paludariums with subdued lighting, freshwater shrimp tanks, or any aquariums with fairly low light levels and moderate temperatures.

 

Aquascaping roundtable discussion: Baliban and Farmer

  By robert | December 5, 2011 - 4:07 pm | Hobby News
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Aquascaping roundtable- This coming friday at 7pm PST, Under the Sea radio will have the great pleasure of presenting TWO influential hobbyists: Jason Baliban and George Farmer! Jason is an American hobbyist recognized as an accomplished aquascaper, and George Farmer is a writer for Practical Fishkeeping magazine and an accomplished aquascaper from the UK. Together we will cover the basics of aquascaping with plants for someone new to plants or aquascaping. People can call in live to ask questions, or email their questions. This is going to be SO cool! I hope you will join us.

http://www.blogtalkradio.com/show3.aspx?userurl=wm-aquaculture&year=2011&month=12&day=10&url=plants–aquabotanic

Here are some photos of Jason Balibans’ aquascaping:

 

And here is work from George Farmer

 

 

Ferns and Anubias

  By robert | December 2, 2011 - 3:03 am | Aquarium Plants
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by Robert Paul Hudson


African Bolbitis fern

When a young aquarist, or anyone new to the hobby, begins to investigate how to keep aquatic plants successfully in an aquarium, that person can feel daunted by the science and cost involved. Do not fret! There are simple, hardy plants! I have found ferns and Anubias together create an intriguing display with little effort, special care or major investment.

Water Ferns are perhaps the easiest of any aquatic plants to keep because they require minimum lighting standards, absorb most of their nutrients from the water, and can grow without adding supplemental CO2. I have found them to be able to tolerate a wide range of water conditions and temperatures. There is nothing plain about the willowy, delicate leafs, or the dark, rustic shapes of ferns.

Reminiscent of the houseplant philodendron with its sturdy oval or elongated shaped leafs, the Anubias provides the needed contrast of strength when placed with ferns. Before I get into the details of a set up using these plants, I will give a brief description of each plant.

Java fern

 

Java Fern, Watersprite, and African Fern

Java Fern , Microsorium, is perhaps the most well known and most recommended plant for low light level set ups. Because leaf stalks grow from a rhizome root that can be divided, and new plantlets also form from the older leafs, it is an easy plant to reproduce. Sometimes a layered effect is created with new plants growing on top of each other. The Wendolv hybrid grows more quickly than other Java Ferns.

Java Fern should be attached to wood or rock so that the roots can access nutrients direct from the water, not the “substrate” or gravel. Poor conditions can cause the older leaves to turn black and begin to decay, but even under these conditions, new baby plants will begin to come to life from the decaying leaves.

Watersprite, Ceratopteris, is the most prolific water plant, growing very quickly under most any condition. The plant may be rooted directly into the substrate, but will grow as a floating plant, or attached to wood or rock. Cuttings are made from the elbows at the point the stem branches and where roots develop, or from the plant tops. Often mistaken for Water Sprite by retailers because of its simularity, Water Wisteria, a hyrgrophila specie, is not considered a low light level plant and should be avoided in this set up.

African Fern, Bolbitis heudelotii is an exotic looking fern with dark green deeply grooved leafs growing from a rhizome as Java Fern does and requires a bit stronger light. The main root can be divided to create additional plants.

 Anubias congensis

 

Anubias

Anubias is a slow growing broad leafed plant with thick leathery green leaves from a rhizome. There are several varieties that vary somewhat in size or shape. Because of its slow growth, it can do well in setups that have a limited amount of CO2 available, but it does need a rich source of chelated iron, macro nutrients, and trace elements. Requiring only a low to moderate light level, it will grow faster with stronger light, if CO2 and additional fertilizer are also increased. There are various supplements that are made for the aquarium substrate that provide iron, (such as laterite, a tropical clay), or supplements that can be added to the aquarium water. Red clay, or clay enriched subsoil can be used in small amounts, (about a one inch layer in the middle of the substrate.) Anubias roots will attach to nearby rocks or wood, but I prefer to plant it into the substrate to draw nutrients. The rhizome should be left uncovered to prevent it from rotting in the substrate. I do like planting small Anubias species, such as Anubias nana, directly to wood when creating a layered, terracing effect.

Here is a typical small tank set up such as what I have done:

  • Size: 25 gallons
  • Lighting: two 20 watt and one 15 watt Trichomatic fluorescent tubes
  • Substrate: Blasting sand and brownish red clay gravel, (Flourite)
  • pH: 7.0
  • Water: bottled spring water
  • Additives: Black Water Extract and trace element supplement
  • Plants: Watersprite, African Fern, Java Fern, Anubias barteri

The bottom substrate consists of two inches of sand mixed with Flourite and a one inch layer of Flourite partially blended with sand on top. Four large Watersprite plants surround a centerpiece of red curio wood that is covered with small Java Ferns and African Bolbitis. In the foreground are two small anubias plants reaching toward the wood pile creating dark shadows under their leaves. The Watersprites create a yellow green backdrop against the dark green Java and African ferns. I have Cherry Barbs and White Cloud Minnows as cohabitants.

Experiment with the placement of the plants and wood, bearing in mind the contrast in color between the Watersprite and the other plants, and because the Watersprite will grow much faster than any of the other plants, it would be more suitable in the background or to the side. Spacing, color and contrast add depth and a three dimensional look to your display. Adding height and depth to the perspective view is easy by stacking wood piles and attaching the plants to the various levels.

How much light do I need?

Light intensity is measured in “lumens” and PAR, however I like to follow a simple guideline that many people have used for a long time: the watts per gallon rule. A low light range is considered 1.5 to 2 watts of standard fluorescent light per gallon of water. For the plants that I have described, I would recommend 2 watts per gallon. A fluorescent with a “kelvin” rating of 5000 to 6500 is preferable in my opinion. Lights should be run for not less than 10 hours a day and not more than 12 hours a day in order for the plants to go through their proper photosynthesis. Fluorescent strip light fixtures, shop light fixtures, or cabinet shelving fixtures can all be used with the proper kelvin type of bulbs.

Substrate

With ferns the substrate material is less important because the plant will take most if not all of its nutrients directly from the water. I have found Anubias to do better with a source of iron in the substrate. There are many sources on the internet and in books and magazines for building a proper fortified substrate for plants. Natural or clay gravel provides a rich earthy brown color that is less stressful to the fish than a light colored gravel or sand. A beautiful aquascape can be created using a combination of various types of wood, such as bogwood, driftwood, and curio wood. Corkbark weighted down has a very unusual look and is an excellent surface for roots to adhere to.

Water Conditions

I have found these plants to be very tolerant of either hard or soft water and temperatures from very cool to very warm in the summer months. If you are not adding supplemental CO2, ideally the water should be soft with a pH of neutral or lower. The ideal temperature is between 72 and 78 degrees F. Soft, neutral water will retain more of the natural CO2, but if adding CO2, alkaline hard water can hold more added dissolved CO2.

I have much larger, and more complicated planted tanks, but this remains one of my most favorite tanks to sit quietly in front of: taking in the simple, but graceful beauty. It is truly relaxing.

Do-It-Yourself Carbon Dioxide Injection

  By robert | December 2, 2011 - 2:22 am | Aquarium Plants
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DIY C02

photo from gpodio.com

By Derek Heath & Len Trigg

Plants have a few basic requirements that must be met if they are to survive and to thrive. If any one of these factors are in limited supply, the others are effectively wasted (and usually algae takes advantage of these leftovers). In an aquarium the limiting factors are most likely to be (in order): light, carbon dioxide (CO2), micronutrients (trace elements), and macronutrients. Micro and macronutrients are usually supplied in adequate quantities by fish waste. Some CO2 is provided by fish respiration, although with heavy aeration the CO2 level will be the same as in the air. If your lighting is sufficient, at least 0.5 watts per litre, the next most important thing you can do to increase the growth rate of your plants is to inject CO2 (and conversely if your lighting is inadequate, injecting CO2 will not help at all).  


Before proceeding with this or any method of CO2 injection it would be advisable that you read up about both plants and CO2 injection. It is especially important to understand the relationships between CO2 concentration, pH and carbonate hardness, and the ways they can be manipulated. (Carbonate hardness should not be confused with general hardness.)

For those of you who have thought of using carbon dioxide (CO2) injection in your planted aquariums but have been put off by either the cost of available systems or have been unsure what the effects of CO2 injection on plant growth may be, then this article describes an inexpensive and easy to assemble DIY system that uses yeast to produce the CO2. The CO2 injection system consists of two parts: a generator which holds the yeast mixture; and a reactor which ensures the CO2 is efficiently dissolved in the aquarium. The two parts are connected by airline tubing.
 
The Generator
The CO2 generator is simply made from a 2 litre plastic soft-drink bottle. Drill a hole through the lid, force some airline tubing through the hole and seal both sides with silicone sealant. Ensure that this seal is airtight. Alternatively you can drill a hole through a rubber bung (bought from somewhere like Para), force a small-diameter rigid tube (perhaps from an undergravel filter uplift) through, and attach your airline to this. Depending on factors such as the carbonate hardness, number & type of plants, amount of surface agitation, number & size of fish, etc. a 2 litre generator should provide enough CO2 for an aquarium of ( 200 litres. For larger aquariums a larger generator or several generators connected together may be required to produce enough CO2.

 
The Reactor
The next step is to build a CO2 reactor. The purpose of a reactor is to aid in dissolving the CO2 in the aquarium water. This can be as simple as using an airstone to produce many small bubbles which will dissolve more quickly than a single large bubble.

Another method is to invert a container, place it in your aquarium and allow the CO2 to bubble up and be collected. The CO2 will remain in this container until it diffuses into the water. It probably pays to have a current directed across the opening of the container to constantly bring fresh water in contact with the CO2.

If you have an external canister filter you can feed the CO2 directly into the intake tube. The time it takes the CO2 to exit the filter should ensure it is totally dissolved. 

Or alternatively you can mount a wide diameter tube (an old gravel vac is perfect) vertically in the aquarium and feed the outflow of your filter or power head down this tube. Feed the CO2 in from the bottom of the tube and allow it to bubble up against the flow of water thus keeping the bubbles of CO2 suspended while allowing fresh water to constantly mix with and dissolve the CO2. Some fiddling may be necessary to achieve the correct balance between tube diameter and flow rate. If the flow rate is too slow the CO2 will collect at the top of the tube, if the flow is too fast the bubbles will be forced out of the reactor. Additional gravel, foam, bio-media, etc. could also be placed in the tube to impede the upwards flow of the bubbles. A very small vent (such as a needle hole) at the top of the reactor is also advisable to allow any “extra” gases such as nitrogen (N2) and oxygen (O2) to escape. The source of these gases can be the original air in the generator which will be displaced by the production of CO2 or if there is a bubble of “CO2” in the top of the reactor dissolved gases may come out of solution in an attempt to equalise the concentrations of these gases between the bubble and the water.

There are probably countless variations on these themes. Where possible make reactors out of transparent materials so you can observe the rate at which the CO2 is being produced. 

 
Setting it going
The final step is to prepare the mixture which will produce the CO2. Dissolve 1 cup of sugar (any type of sugar will work) in about 500ml – 1 litre of water and pour into the generator. Dissolve 1/2 – 1tsp. of yeast (bakers yeast is available at any supermarket) in a small amount of warm (NOT HOT) water, add to the generator and top up to the required level with cold water. It is important that you do NOT overfill the generator. Once the yeast is activated and starts to produce CO2 a certain amount of “froth” will be produced. Enough head room must be left to ensure that this froth is not forced up the airline and into the aquarium. The addition of 1 tsp. of baking soda will help buffer the mixture and extend its working life. It also reduces the amount of froth produced.

If you use hot water to dissolve the sugar allow the temperature of the mix to reach room temp before connecting the reactor. As this water (and the air above it) cools and contracts it may start a siphon going, dumping aquarium water into the generator, if the production of CO2 has not yet started.

The above quantities are not critical so you can experiment with them if you wish. In general the quantity of yeast controls the rate of CO2 production, and the quantity of sugar controls how long the mix will last. Ideally you want a mixture which will produce CO2 at a steady rate for an extended period of time.

This mix should produce CO2 for at least 10-14 days (often longer). As it takes 12-14 hrs (depending on temperature) for a new mixture to start producing sufficient CO2 it is best to get a new batch started 24hrs before the old batch needs replacing. Alternatively you could have two generators producing CO2, one of which is replaced every week. This latter method probably provides for more stable conditions in your aquarium.

 
A few tips and warnings:
In order to maximize the benefit of injecting CO2 it is important that you reduce any surface turbulence as this will quickly allow dissolved CO2 to escape into the air. The best ways to achieve this are to, turn of any aerators, lower any spray bars below the water line, direct the current to run around the sides of the aquarium rather than from top to bottom and/or if you have air driven under gravel filters extend the uplift tubes above the surface of the water. Optimally growing plants will produce more O2 and saturate the water with O2 better than any other method you can try.

An increased CO2 concentration will not displace dissolved oxygen (O2) from the water. It seems to be generally accepted that a concentration of 15-10 parts per million (ppm) is ideal for optimal plant growth and that CO2 concentration must exceed 30ppm before becoming dangerous to fish (although the pH drop caused by suddenly injecting this amount probably will).

Do not unplug the CO2 system at night. At night, with the cessation of photosynthesis, plants become net producers of CO2 and consumers of O2 just like fish. This might lead you to believe that you should disconnect the CO2 at night to prevent CO2 building up. However the pH shifts caused by disconnecting the system will be much larger and more sudden than gradual change when the system is left connected. The rate of CO2 production is also dependent on temperature, so the generator will automatically produce less CO2 at night as it cools. (You may want to try sitting the generator near the warmth of your lights, but beware of potential electrical hazards should a spill occur.)

Sometimes a stringy white growth, of unknown composition, may start to grow on the airstone or end of the airline. It appears to be harmless to both plants and fish (certainly swordtails can eat it with no apparent side effects).

Finally, NEVER try and block or restrict the flow of CO2. The CO2 is constantly being produced so pressure will build up and eventually the generator will explode. At the best you will have one hell of a mess to clean up, at the worst physical injury could be the result.

 
Summary
Adequate light in conjunction with CO2 injection will enable plants to photosynthesize at or near optimal levels. The increased vigor of your plants as a consequence of this will be observed not only in their increased rate of growth but also in streams of oxygen bubbles being released from the leaves (this sight never ceasing to amaze us). In turn your fish will benefit from the increased oxygen concentration and the cleaner water produced by the plants. 

For those of you who are thinking this system is to good to be true, there is indeed at least one drawback. The increased growth rate will result in the need to spend extra time trimming many of your plants to prevent the tank becoming a jungle of growth through which you can no longer see your fish. In the case of some species of plants e.g. Hygrophila polysperma this trimming may need to be done weekly. Fortunately there is a ready market for these cuttings from pet shops and fellow club members.

The yeast system described requires some care and maintenance, but is an excellent and inexpensive way to experiment with CO2 injection. May your plants live long and prosper.