Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
Average activity level fish: 3" max. And not too many of them. Smaller is better.
Fish that are highly active, especially horizontal fast swimmers: 2" max (and even that is pushing it)
Sedentary fish: 4-5", but remember the bioload goes up with the CUBE of the length. One 4" fish produces EIGHT TIMES the waste of a 2" fish.
These are rough guides, but I sure would not put larger fish than this in my 29 gallons.
Pearl Gouramis- slow moving, territorial- only get one
Angels- a breeding pair and NOTHING else.
Carnivorous bottom cats- Banjos and others- Some are more social, and are OK with friends, but the bio load of carnivores is higher than herbivores. Will eat smaller fish.
Algae eaters such as Loricariads- Well, they produce a large volume of waste, but it is mostly plant material, not as high in nitrogen as carnivores. Just unsightly. Many of these are high oxygen fish, so need plenty of water movement.
Fast swimmers like the mid sized and larger Rainbows are a bad choice (even though some are only a little over 2") because they are highly active. If you want fast movement stick with the smaller species such as Zebra Danios.
Chubby little fish like Upside Down Cats, Cories, Ruby Barbs and similar fish are probably a better choice. Most of these are slower moving.
Kuhlie Loaches are small enough that their high activity level is OK in that tank. Most of the other loaches are chunkier, and demand high oxygen, so only the smaller ones would be good. Sids, Zebras.