Fish FAQs

How many fish can I keep? 

Fish need space to move for good health, and overcrowding promotes disease. As long as you’re sticking to fish with an adult size of two or three inches at most, a handy rule of thumb is “one inch of fish per gallon of aquarium” - that is to say, in a ten gallon tank, you could safely have five two-inch fish, or three three-inch fish. Click here to learn more about fish selection. 

Help! My fish are sick!

Treating sick fish in an aquaponic system can be tricky, because many of the medications and treatments used in aquariums may not be safe for your plants, especially if they’re plants you intend to eat. Prevention is the most important tool you have: always quarantine new fish in a separate tank for several days before you add them to your system, and do your best to keep your water clean and healthy, with low nitrates and a stable temperature and pH.

If you do see sick fish, your best bet is quarantine, again; if you can pull out the sick individuals and put them in a separate tank, you can medicate them there, and you may be able to stop the disease from spreading to other fish.

Finally, if your fish are suffering from ichthyosporosis - one of the most common aquarium fish diseases, and distinctive due to the appearance of small white nodules like grains of salt on the fish’s fins and scales - you may be able to stop the disease by increasing the temperature of the water. “Ick,” as it’s known, can’t reproduce at temperatures over 30.5 °C, so turn up the heat!

What can I do if algae starts growing in my tank? 

Even if you’re careful about the amount of direct light your tank receives, you might find algae growing in your aquarium from time to time. This is harmless in itself, but nobody likes being unable to see their fish!

Algae can be a useful indicator, however; lots of algae growth can indicate that your system is holding a lot of extra nitrate, which can be unhealthy for your fish over time. The first thing to do if you’re having algae trouble, other than using a clean glass scrubber or cloth to scrub it away, is to test nitrate, and to perform partial water changes as necessary until your nitrates are below 10 ppm. You may also need to reduce the amount you’re feeding your fish.

A stable system will also be more resistant to algae growth; bigger, better-established plants will be better at taking up more nitrate, more quickly!