Helping you keep your aquarium beautiful and healthy


Big Tanks, Little Fish

by Robert W. Bly, founder,

It's every aquarium hobbyist's dream: add more and bigger tanks, moving up to new sizes you've never owned before.

Typically, when the aquarist gets his first big tank, his immediate thought is to put big fish in it.

I did that for years with specimens including Jack Dempsey Fish, Oscars, and an Arawana.

But recently I've found a new joy in my aquarium hobby.

Instead of filling my big 92-gallon corner tank with a few big fish, I've filled it with dozens of smaller fish.

And I love it!

Mario, the local pro who cleans my tank occasionally, saw it the other day.

"Wow, this is beautiful," he said in tones of genuine envy.

Mario has big tanks, of course ... but they are filled with only a few big fish.

Yes, big fish hold a certain fascination for aquarium keepers. But the larger the fish, the fewer you can have in the tank, and therefore the less variety.

For instance, when we were shopping for a custom saltwater tank (on the wish list and as yet unpurchased), my sons asked about a small shark.

The dealer discouraged this, saying that if they put a shark in the tank, that would be basically all they could have.

A cichlid devotee all my life, I am now a fan of lots of small fish in big tanks.

Among the highlights of my newly repopulated big tank of small fish:

  • A small fire eel. He used to stay buried under the gravel as eels do, and we'd never see him. So we put in a cave-style decoration. He has taken up residence, and now we see him all the time.
  • A large freshwater shrimp. He also used to move around and was hard to spot. Mario leaned a slab of stone against the wall of the tank forming a lean-to, and now we can usually find the big shrimp by looking there.
  • A monster-size 9-inch pleco - a left-over from when the tank housed large cichlids. He dwarfs the other fish, but he's a gentle giant who never bothers them. We have named him "Gigantor."
    We also bought a small orange-spotted pleco, which because he is a fancy fish, cost more than the big one.
  • 20 neon tetras that swim as a school and hang out in their own territory toward the bottom back of the tank.

The rest of the tank is an assortment including tiger barbs, rainbows, two glass catfish, danios, gourami, and a pair of deep red swordtails.

We have a sump type filter where water to be filtered flows from the surface down a vertical plastic chute inside the tank.

The water is conveyed to a filter at the bottom where it is cleaned and then pumped back into the tank.

I would not recommend this set-up, as smaller fish follow the current, swim over the lip of the plastic chute, and end up in the filter.

They seem to live fine in the filter, so we now check every week, and if one has been trapped, we rescue him with a net and put him back in the tank.

The rule of thumb for aquariums is one inch of fish per gallon of water. If your average fish is an inch long, a 92-gallon can hold over 90 fish.

We don't have half that many, and don't plan to. But note that I say "plan." The fish store is a constant temptation for me: if I walk in and see something I like, I want to buy it.

And with my big tank now dedicated to small fish, I can, as long as it's compatible with what I already have on the tank.

Action step: keep on your PC a written inventory of the fish in your large tanks. When you go to the fish store to browse, bring the list with you. If something tempts you, show the list to the fish dealer to make sure that fish can live in harmony with the other specimens in your tank.