10 simple rules for a healthy aquarium


Clockwise from top: Chad, Wagatha, Pearl (trailing a truly impressive string of poop), and Miss Chanandler Bong. Spot was enjoying some alone time down at the bottom of the tank.

In a comment on my first aquarium post, Mike wrote,

I just skimmed the page about cycling an aquarium. This was a healthy reminder of why I don’t attempt to keep fish — the whole process seems terrifyingly complex.

I commented that fishkeeping only seems terrifyingly complex – it actually runs on a handful of guidelines that almost always work. I started writing them out in the comment, and when I got them all down, I cut them out and pasted them here. Without further ado:

Matt’s 10 Rules for a Happy Aquarium

  1. Be patient. Start small, with many fewer fish than the tank will ultimately support, until the nitrogen cycle is up and running (I guess knowing about the nitrogen cycle is step 0).
  2. Start with hardy, inexpensive fish, that can withstand some swings in temperature and water chemistry. In practice this often means fish that evolved in crappy environments, and fish that are good at establishing new populations. Ancestral platies are from shallow streams in Mexico, and there are introduced platy populations in Florida (expected), Singapore, Hong Kong, and Montana (whut), so they’re pretty tough. Get a fish book and learn the basics about some prospective boarders.
  3. Make sure the temperature of the tank suits the fish. Goldfish do best in the 50s and 60s Fahrenheit, tropicals in the 70s to low 80s. Some fish are picky and have narrower ranges – those fish are usually picky in other ways and are not good starter fish. See the fish book.
  4. Give some thought to how fish get along with others, or fail to. For schooling fish, get small groups rather than individuals. Don’t keep fin-nippers like tiger barbs with long-finned fish like angelfish and bettas. How will you know which are which? See the fish book.
  5. Realize that almost all pet-store fish are young juveniles and they will grow, so plan for the adult size, not the size-at-time-of-purchase. For the adult sizes – see the fish book.
  6. Don’t overcrowd – one inch of fish per gallon of water is a good target once the tank is fully up and running. If you want 15 to 20 fish, get a 15-to-30 gallon tank, start with 5 fish, and build up patiently. See the fish book.
  7. Don’t overfeed – give only as much food as the fish will entirely consume within 5 minutes. See the fish book.
  8. Do filter heavily. IME it’s hard to over-filter. I started out running big-ass filters because I was keeping aquatic turtles that generated a lot of waste, but those big filters kept the tank looking good even when I had no turtles. The more biological filtration – letting the water run over or through filter media with crud growing on it – the better. See the fish book.
  9. Keep live plants, the more the better. First because they’ll outcompete the algae and you’ll spend much less time scraping the tank. If you have live plants and a snail or plec, your scraping time may be zero. I’ve never scraped algae in my life, and I never will. I’d rather buy a cheap bundle of anacharis and a snail and never worry about it again. Second, because the more complex and diverse the tank ecosystem is, the better it will be buffered against all kinds of maladies, from chemical imbalances to bacterial blooms to parasites. Not all fish books push readers to keep live plants, but most do.
  10. Accept that even if you do all of that stuff, you’ll still lose the occasional fish, especially when you’re first starting out. Those hardy fish from crappy environments are strongly R-selected so although they are tough they are also evolutionarily disposable and they die at odd times, often for no detectable reason. Accept it and move on. In the same way that one builds a body of work by publishing one thing after another, one remains a fishkeeper by not quitting when fish die.

I rather snarkily added “See the fish book” to as many entries as possible because all of this stuff is covered in any intro fishkeeping book. There are zillions of these on the market, and any of them are probably good enough for someone starting out. I prefer older, more comprehensive works. A printing of Exotic Aquarium Fishes by William T. Innes from the 1960s or 70s can usually be had for a buck or two (example), and it will have a LOT more useful biological data than the newer, flashier titles.

Now, compare all that to what far too many aspiring fishkeepers actually do: get some crappy little 1- or 2-gallon nano tank or betta bowl, put in a couple of goldfish – which would maximally stress an established, cycling 5-gallon tank, let alone a brand new nano tank – and no live plants, with probably inadequate filtration and no temperature control, and then be shocked and disappointed when the fish get sick, get parasites, and die. When 5 minutes of online investigation would have led them to any of a zillion advice pages like this one.

It’s just like stargazing or most other hobbies – you can avoid most of the frustration for a trivial outlay of research time.

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4 Responses to 10 simple rules for a healthy aquarium

  1. Mike Taylor says:

    Idea for the next post in this series: expand on “Get a fish book”.

  2. Mike Taylor says:

    “One inch of fish per gallon of water is a good target once the tank is fully up and running.”

    It pains me to see a linear measurement of fish related to a volumetric measurement of water. Surely a three-inch fish needs much more than three times as much water as a one-inch fish (if not necessarily 27 times as much).

  3. Andy Farke says:

    Good advice all around in your post!

    Farke’s Corollary: Don’t even think about a salt water tank unless you are ready for that responsibility. I don’t have one, but know people who do, and it’s a real time and money sink, and can be quite finicky. Which is fine if you’re into fish as a serious hobby (and that’s totally cool), but less fine if you just want the casual fish tank experience or not have to worry about everything going dead if you look at it funny.

    I would also add that for equipment, you don’t need to go hideously expensive, but for some stuff it’s worth buying a notch or two up to avoid frequent turnover or massive problems. I’ve found the el cheapo aquarium heaters to be not worth the savings — they are prone to ratcheting up your tank temp waaay too high if you bump the little knob, and tend to not last as long as they should, either. My filter system has lasted since Day 1, though.

    In terms of algae management, I still have to scrape every 2 weeks or so. Our house has lots of windows, so it’s hard to avoid a bit of accelerated growth, especially in the sunnier and warmer months. Maybe I’ll buckle down and get a snail at some point.

  4. Matt Wedel says:

    Idea for the next post in this series: expand on “Get a fish book”.

    I thought I had – get the Innes book. Any book published in the last four decades will have more color photos, but fewer pages (probably many fewer), less text, and far less useful information.

    It pains me to see a linear measurement of fish related to a volumetric measurement of water. Surely a three-inch fish needs much more than three times as much water as a one-inch fish (if not necessarily 27 times as much).

    I think it’s balanced out to a large degree by the higher activity levels of the smaller fish. If a 5-inch fish swam as rapidly and as constantly as our platies, it would probably catch fire.

    Andy, I fully agree on the salt water and on getting by with inexpensive gear. Like you, I’d rather run with a cheap filter (anything that pushes water through the filter media, basically) and a nice heater than vice versa – I’ve seen too many horror stories of people who came home to a tank of fish stew when their $10 set-it-and-forget-it heater malfunctioned. So far our new tank is holding steady at 75F so I’m running heaterless for the moment.

    Maybe I’ll buckle down and get a snail at some point.

    Do it! Mystery snails are so cool. They won’t molest your vascular plants and they are hell on algae. I reckon a plec is not a good option for you – apparently they don’t get along well with other suckers/bottom feeders, which would potentially put your cories at risk if you ever got one. But a snail should be fine. It will probably grow a bunch while it’s in your tank, and because it will be getting a slightly different nutrient cocktail, the new shell growth will be visibly different from the old. At least, that’s always been my experience with them.

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