Noted, but I can’t see them getting that much bigger!
If they are healthy, and in the right environment, they should attain over 1 inch, generally close to 1.5 inches, and sometimes even 2 inches. In aquaria they tend to remain around 1.5 inches. If essjay's dimensions (post #4) are correct, this tank is fine.
There is more to keeping fish that mere tank size and fish size ratio. This is a fish that lives in congregations of hundreds, even thousands, in flooded forests for half the year. It "expects" things, and to be in the best of health, it must be provided with something similar. Now, we can't all have a tank with several hundred (I have seen this, quite stunning) but keep it in mind.
What about groups of cpd’s and lamb chop rasbora, etc or will they end up attacking my cardinals, I’ve almost given up on the community tank idea
The Celestial Pearl Danio, definitely not here. On their own in this tank, yes. But not with cardinals or anything else in this small a space.
The lamb chop rasbora (
Trigonostigma espei presumably, or perhaps the closely related and in my view more striking
T. hengeli), yes, as far as with cardinal tetra. The rasbora remain in the mid to upper level, the cardinals tend to be mid to lower level, so a good combo from that aspect. Then we come to the tank size. A 29g (30 by 12 by 18 inches) would be ideal for both, plus some substrate cories etc.
Community aquaria are involved, as there are so many aspects to consider in order to provide the best conditions for each species. We need to remember that very rarely are the species we put into a community aquarium ever together in their respective habitats. Just because they are all "fish" does not mean they are going to thrive together. And surviving, which is sadly the best so many hobby fish can expect, is not at all the same thing as thriving.
