Jamie Lawrence

Tropical Fish

Why you should/shouldn’t listen to me

I bought my daughter a fish tank when she was about 5 or 6. In a pretty predictable turn of events, I was the only that looked after the fish, and replaced them when they died, and read-up on how to stop them dying. Eventually, that childish 35L tank was replaced with a 120L tank of my own.

I’ve been keeping tropical fish 2014 (or before—memory is hazy) and now have two tanks: a 200L “community” tank and a 20L nano aquarium. Both are tropical and I mostly stick to “easy” fish and plants.

Tropical or Cold water?

Quick primer: goldfish are cold water (don’t need a heater), and most other fish in the shop will be tropical (need some form of water heater).

The immediate assumption is that tropical tanks are considerably more expensive and complex than cold water tanks. That’s generally not the case. Cold water tanks also need some form of filter (do not buy a “bowl”) so the main difference between cold water and tropical tanks is just the heater. The heater is literally the easiest thing in the tank: just set the temperature and position it in the tank! Not complex at all!

The other downside to cold water tanks are the fish you can keep: basically, goldfish. Goldfish are pretty big fish, and big fish are dirty fish (they poop a lot) so they need a bigger tank and more water changes. A tropical tank opens up the world of much smaller fish—so you can keep more in the same space—and much more colourful and interesting species.

There is a third main type of tank, the salt water aquarium (for ocean-dwelling fish), but I can’t speak about those from experience.

In my opinion, buy a tropical tank as your first aquarium. They’re no more complex than a cold water tank, simpler than a salt water tank, and opens up a large variety of pretty fish.

Buy the biggest tank you can

This also seems totally unintuitive but bear with me: A bigger tank is better, it’s easier to maintain, easier to start, and more likely to keep your fish alive. Fish aren’t designed to live in small bodies of water and, unlike in the wild, all their waste stay in this little tank. Buying a bigger tank means you’ll have more water. More water means smaller temperature swings, long times between water changes, smaller water changes.

I’ve previously owned a 35L tank (our first, for my daughter), and a 120L. I currently have a “main” 200L and a small nano 20L tank in the office. The 200L is much much easier to maintain! The 20L needs a water change every week, whereas the 200L probably only needs one every few weeks. The 20L suffers from temperature swings, the 200L does not (e.g. in a short power cut). The 20L houses 1-2 fish, the 200L has 25+. I really couldn’t keep any fish alive in the 20L tank without the 5+ years of experience with fish keeping—and I still lose fish in it ☹️.

So buy the biggest tank you can a) afford, b) house comfortably and c) access for regular maintenance. You’ll need to change about 10%-20% of the water volume so bear that in mind. For a small 30 litre tank, a 5 litre water bottle is enough to perform a water change. For a 200L tank, you’ll need at least a 20-30L container which gets very awkward to move around (remember: 1L = 1kg, so that’s 20-30kg of water) and a more major water change might involve several trips.

I think I’d probably tell someone that a 60L would be the smallest tank to start with but 100-200L is an even better place to start.

Keeping water


There’s a phrase in the hobby about “it’s not so much keeping fish as keeping water” and there’s truth to that. You need to understand the nitrogen cycle. You need to take regular measurements of the main pollutants (ammonia, nitrite, and nitrate).

I have only just come to terms with the fact that my water supply is way too high in nitrates to be good for keeping fish. Out of the tap I get about 40ppm of nitrates which explains a lot about my early struggles with keeping fish and my persistent problems with algae.

Bacteria are good, sterile is bad




My favourite fish


I’ve had terrible problems keeping the ubiquitous Neon/Cardinal Tetras. They die off quickly or they cling on forever but in a deformed state. Guppies are pretty hard for me to keep but I’ve had one stowaway female for over a year—my theory is she’s lived so long because she hasn’t been pestered to death by randy males. I’ve kept them in high female-male ratios and they’ve bred (being pregnant is basically their constant state).

Rasboras are amazing in a group of 10-15 but my school quickly dwindled and I never knew if the Black Widow tetras were eating them or the high nitrates got them.

Corydoras are interesting, funny to watch, extremely peaceful, and helpful cleaners. They great in a group. I currently have Sterbai Corys but I think my favourite are a large group of 10+ Panda Corys.

Tetras are an “easy” fish to start with and I really enjoy the Black Widow Tetras in a larger tank. The Serpae Tetras are some of the most colourful “easy” tetras. The Rummynose Tetras are a beautiful schooling tetra.

Nothing beats a Betta. If a fish could be an excitable puppy, then that’s what a Betta is. They’re always eager to see you in the morning, always curious, will eat food off your fingers and are generally just an amazing fish to keep. I use a modified Fluval Flex V to keep them in my office but think I’d prefer a 30-35L tank so I could also keep a few Corys with it.

Fish die


When there’s no hope


There’s no “good” way to euthanise a fish. I’ve tried drops of clove oil in some water to put them to sleep but I haven’t found it worked especially well. I even beheaded one poor fellow and whilst effective it’s too traumatic for me.