keeping an aquarium

m. werneburg, 2016.12.22

the politics of keeping tiny fish

We owe it to the fish we keep to do a good job. Keeping an aquarium is an odd hobby in which you use living things as ornaments. I suppose there are probably people who consider it inhumane for that reason. But the point isn't to parade some beautiful little creatures in a moodily lit display environment. Instead, you're raising those critters in an environment that they, too, find pleasant.

Yes, it's likely that we've created stunted subspecies by providing unnatural surrounds free of terrorizing predators, surging currents, droughts, and starvation. Worse, we breed for uselessly long fins, unnatural color combinations, and stunted size. And by in-breeding our stock with other captives, we weed out the hardiness and even distinctive behaviors from the poor little things. For instance, the ubiquitous angle fish of our aquariums has forgotten how to raise its young, and no longer bothers.

So I think it's all the more important to do our best to keep balanced aquariums in which robust species live in neither torpor not terror, with some stimulus but a great deal of respect for their natural state.

keeping a stable aquarium

keeper fewer fish than you'd like

Keep as few fish as possible, in as large an aquarium as you can keep. The aquarium below is a very small one, barely more than a hospital tank for a single recuperating fish. And that's how it started out. But I found myself using it so much that I got some gravel and a stand and a hood, and by that point I decided I'd need an outside filter and some further ornaments and some live plants. Now look at it!

That aquarium has, at present, only two tiny fish (both of the aforementioned stunted varieties). One's a dwarf gourami, which lives near the water's surface. The other's a suckermouth catfish, one of the countless plecostomus varieties that gnaw on drift wood and also algae. For several months, there were two gouramis, but one died (from neglect/starvation while we were away for three weeks). But that was it. About five or six "fish-inches" in a 15 gallon tank (12—15 fish-centimeters, 60L).

There are several reasons for keeping so few fish. First, it keeps the pressure off; nothing likes to be crowded. Yes, many species like to hang around with a minimum number of their kind, but if you only have room for a small aquarium you can't keep those species. Keeping few fish also means limiting potential conflict between incompatible species.

Second, it keeps the water much more stable. There are tools online such as this handy advisor that will tell you when you've overloaded an aquarium, and you should listen to that advice. It is harder to keep a small aquarium stable than it is a large one, because small mistakes have a larger impact on the smaller aquarium (and you will make mistakes). You'll note, for instance that in addition to all the plants, I have both a sponge filter and an outside filter on that aquarium. This is to ensure that the nitrogen cycle is as strong as possible: the wastes produced by the fish and by rotting food and plants can be converted to relatively harmless chemicals, but there have to be populations of two separate thriving bacteria species for that to work, in addition to oxygen supply (bubbles, plants, spilling water) and mechanical filtration (all that sponge and floss media).

In fact, the easiest way to avoid those mistakes is to start with an empty aquarium that you let settle in; then add a small number of fish and let the system re-balance once again. This isn't as much fun as setting up an aquarium from scratch and dumping in some fish, but it's true aquarium-keeping: the fish introduced in a leisurely fashion will survive. The others won't.

Third, it makes life a lot easier when you're not trying to keep water within the 2°C band tolerated by eight species crammed in a community aquarium, or trying to find a pH balance that suits that many species. Use tools like the "advisor" linked above to find a mix of species that naturally tolerates the same range of water conditions, and you're good.

place the aquarium with care

Fish prefer dim lighting, shelter from above, and plenty of hiding spots. The very opposite of the "display" type of aquarium we like to look at. So let's work with the fish by placing the aquarium away from stressors like distractions, light, temperature fluctuations, and so one. Avoid direct sunlight at all costs—the fluctuations in heat or light can be fatal in of themselves, but warm water tends to encourage plant rot, and the light encourages algae. Under these conditions, the nitrogen cycle can become unstable.

Avoid areas with busy traffic—places where humans frequently pass can feel like predator-strewn nightmares to tiny fish.

Avoid areas where the aquarium will be neglected. I know, I know—just try reconciling this with the previous two dictates. But it's true; a forgotten aquarium will turn into a death pool.


To maintain a stable aquarium, there are a variety of odds and ends you'll need to use:

In the setup above, there's already a good filter, a good heater, and a good air pump. The pump on the aquarium in the photo above is a bio-wheel unit, but I think those are essentially a gimmick and recommend a standard "Aqua Clear" or something similar. Look for a submersible heater with a temperature adjuster, and spend as if you'll be replacing them every two years—they're unstable and nowhere near as durable as the the components with moving parts(!). I tend to leave the air pump sitting on a small towel to absorb vibrations.


reader comments

Hi Michael, thank you for trusting us with this tank! Everyone has settled in for the night and seem to be quite happy. We have named them Daisy and Oscar :) Our one cat didn't leave the room for an hour ... she is not sure what we have brought into the house!! We will keep you posted on how it is going, Jule-Anne and Angus


Great names!

The aquarium's in good hands. As we were hauling things in, a neighbour told Angus that he would Angus some fish. Angus suggested instead that the aquarium would need a settling in period, and that anyway, it was too small for many more fish. Exactly what he should have said! 8^D