FUNCTIONAL FISH FOR A SMALL, LOW-LIGHT AQUARIUM

A fishy tale 

By Bruce Lucas

INTRODUCTION

A friend of mine who worked at a pet store talked about these fish called "oscars" that ate goldfish. They sounded cool. I told him I had to get some of these just so I could feed them goldfish. He told me to come in and buy a tank and he would give me a "discount" on the rest of the equipment. A five-finger discount that is. Yes, we were in high school.

So there I was with my first pet fish--3 juvenile oscars in a 10 gallon aquarium. Rather than tell a horror story which involves my complete ignorance of the nitrogen cycle and their eventual move to a 55 gallon aquarium which still was not big enough, I will tell a happier, more peaceful story.

The apartment complex I now live in allows a maximum aquarium size of 20 gallons. This does not give much room to work with if you desire a variety of fish. I wanted lots of fish swimming around, but did not want the fish to suffer in pollution. Been there, done that. The (now) obvious answer to the dilemma is a well-planted aquarium. I read about all the high-tech gadgetry available, but the capital cost turned me away. So I was pretty much stuck with a small, low-light, and relatively low-tech planted aquarium.

Here is a summary of my constraints:
· Small aquarium size: 20 gal (24" L ´ 12" W ´ 18" H)
· High fish count: crowded aquarium with 15 to 20 fish
· Low light: normal output fluorescent light supplied at 20 W/ft2 or 2 W/gal (40 W total)
· Low carbon supplementation: Seachem Flourish Excel dosed at 0.1 mL/gal/day (2 mL/day)

INITIAL SETUP

The first plants introduced were amazon swords (Echinodorus bleheri), java fern (Microsorum pteropus), and java moss (Vesicularia dubyana). These all showed satisfactory growth under the 40 W of normal fluorescent light. Do not ask about my attempts to grow plants in the old oscar tank.

Regarding lighting, "they" fooled me in the beginning though. I bought specialty aquarium tubes: Coralife Nutri Grow Plant Lamp and Coralife 50/50 Fluorescent Lamp. Sure, my plants grew well, but I could have achieved the same results with $5 GE Plant & Aquarium or GE Sunshine tubes instead. Lesson learned. Stay away from the overpriced $10-20 tubes. Any benefits they may provide are not worth the extra money.

The only good thing about the Coralife 50/50 tube was how amazing it made my neon tetras look. I started with a dozen neon tetras. They were 5 for $2, plus every now and then you get a free one from the local fish store. I suppose it was the actinic blue that made them so eye-catching in my tank. The neon tetras pretty much glowed.

Along with the neons, I bought corydoras catfish. They stay small and keep to the bottom of the tank except when getting air from the surface. Their size was their big selling point for me. I did not want another fast-growing catfish like the blue channel catfish I used to have. The blue channel catfish was with the oscars of course.

I decided on 3 leopard corydoras (Corydora julii) and 3 panda corydoras (C. panda). It turned out that what were sold as leopard corydoras were really three line corydoras (C. trilineatus). Two of the panda corydoras died and were replaced with 2 peppered corydoras (C. paleatus). The pandas are well-known to be delicate, while the peppered have a reputation for being extremely hardy.

Now I had a dozen fish swimming in the middle and top sections of the tank along with a half-dozen fish swimming along the bottom of the tank. Everything was fine now, right? Wrong.

BIG PROBLEM

A new dilemma presents itself. The high number of well-fed fish is a considerable source of waste, particularly nitrates. There are low-light plants (e.g. Hygrophila polysperma) that will grow at a steady pace which require regular pruning, but they will not be big enough sinks for all of the nitrates. Algae-free will not be a suitable term used to describe this aquarium. There simply is not enough light and carbon available for the plants to utilize all of the nitrates and other waste products. Floating plants may be able to get around the carbon and light shortages, but they would shade the tank, which I do not want.

PRACTICAL SOLUTION

After a case of ich decimated the neon tetras there was an opportunity to create and enforce a new policy on selecting fish. I decided to simply stock the tank with fish that serve a functional purpose in the aquarium. For the most part, this means having a variety of algae eaters. This makes sense anyway since there is not a single fish (at least not well-known and readily available) that eats every type of freshwater algae, stays small, and does not harm plants. If there was, then I am sure its common name would be Holy Grail.

There are other functions that may be met by aquarium fish including snail eater, water quality indicator, and scavenger.

The chosen algae eaters were otos (Otocinclus sp.), a bristlenose pleco (Ancistrus sp.), rosey barbs (Barbus conchonius), and cherry barbs (Puntius titteya). A yo-yo loach (Botia lohachata) got the job for snail eater. The rummy nose tetra (Hemigrammus bleheri) serves as a water quality indicator. The surviving corydoras get to stay since they will scavenge.

Here is a brief overview of the fish I chose and specifically what they are good for. You can find additional details elsewhere.

Otos
I keep 6 otos in my aquarium. I started with only 2 to get rid of brown algae on the glass and some plants. They will also consume soft, green algae. I added more to keep the green algae in check. Six is probably the minimum number you want to have, even in a small tank like mine. Younger ones seem to be more active during the day whereas older ones are shyer. Even the shy ones eat their share of algae. You just do not see them do it. Their fat, round bellies are evidence of that.

Bristlenose Pleco
I recently added a bristlenose pleco to consume more algae in bulk. Think of it like a super-size oto. Its big mouth will clear wide paths of algae compared to the smaller mouths of the otos. It may have trouble eating algae from the tip of long, slender leaves due to its size. The otos can take care of the tips. A clown pleco is an alternative to the bristlenose pleco, but it is debated whether a clown consumes as much algae as a bristlenose. Both maintain a small size suitable for a small aquarium.

Rosey Barbs
My 3 rosey barbs were brought in to take care of hair/beard algae that threatened to take over the tank. They seem to be constantly hungry, which is just fine with me. It does not take them long to eat away at the tough to remove algae until it is out of sight. Siamese algae eaters are a more well-known alternative for eating these types of algae, but they are not as readily available as rosey barbs. They can be aggressive towards each other at times, but I have not noticed any inflicted damage. If the tank was bigger, then I would get at least a couple more.

Cherry Barbs
I tried 3 cherry barbs before the rosey barbs to attack the hair/beard algae. Maybe they ate some and maybe they did not. I do know that they were not up to the challenge of keeping it in check. They also nip at java moss, but the java moss grows way faster than it can be eaten. I suppose it was the same way with the case of hair/beard algae in my tank. They are smaller and more colorful than the rosey barbs though. Keep a mix of males and females (e.g. 1 female with 2 males) if you want the males to maintain their bright red color. They are tougher than neons too.

Rummy Nose Tetra
I once saw an article about discus, which recommended keeping rummy nose tetras with the discus. The reason is that the rummy nose's bright red nose will fade in poor water quality. So I added a rummy nose tetra to clue me in to any disastrous problems. After I know for sure that I will not make any significant changes to my tank and no problems arise for some time, I will probably remove the rummy nose.

Yo-Yo Loach
Whenever you add plants, you run the risk of adding snails too. The yo-yo loach is a snail-eating machine. Without supplemental food tablets, it will continue to eat all snails in sight. They also keep a small size with a slender shape. When you hate pond snails in your tank, it is quite a sight to see empty snail shells littering the substrate. My loach is a bully at feeding time. Perhaps a month or so after I finish experimenting with new plants in my aquarium, I will try to catch the yo-yo loach and put it elsewhere. Try.

Corydora sp.
The different corydoras in the tank will all scavenge the bottom of the tank in search of food. They are not left solely to scavenge. They are fed 6 nights a week. In case any flakes or micropellets fed to the barbs and rummy nose find their way to the bottom of the tank, the corydoras will surely take care of them.

MAINTENANCE
Here is the maintenance breakdown for my aquarium:

Daily
· Dose 2 mL of Flourish Excel in the morning.
· Feed the barbs and rummy nose once in the morning.
· Feed the corydoras once at night.

Weekly
· Change 1/3 of the water to reduce nitrates from 20 ppm to 10 ppm.
· Prune the stem plants and toss out handfuls of java moss as needed.
· Throw in a slice of blanched cucumber, which lasts two days.
· Dose KCl (20 ppm K) and MgSO4×7H2O (5 ppm Mg) (twice a week)

Bimonthly
· Break 2 houseplant fertilizer sticks into 3 pieces each and distribute them throughout the tank under the sword and stem plants.

CONCLUSION
It is possible to have a small tank which is: (1) low-tech so it is relatively inexpensive to setup; (2) have a variety of plants, some of which grow fast and some which do not; (3) have several varieties of fish each bringing its own color and charm; and most importantly, (4) keep algae in control so you can spend more of your time observing your fish than cleaning up their home. I do not scrape algae off the glass or the plants. There is always some kind of algae present in the tank, especially on my slower-growing plants, Cryptocoryne wendtii and Anubias barteri var nana, but I leave the fish to take care of it for me. Since algae are not a concern anymore, I am free to increase the variety of low-light plants including the slower-growing species which might otherwise suffocate under a blanket of algae.