Originally Posted by Tikibirds
I have never done a bigger tank with several species outside of female bettas and I want to have another species or two in my 20G. I don't want to overload the filter by adding too many at one time. What I want to know is about how many new fish can I add at once? Is there a general rule or anything. Im thinking its gonna be some type of cory and I know they like groups. Diamond tetras would be nice too but I was told I needed like 10 of them
When I add a new fish, depending on the size, I add 3-5 more. I mean it's all up to the tank size and fish size. If I were to have a 150g tank and I was putting cardinals in there I'd do 30 at a time! However if I'm adding larger fish like a pleco in a 30g I'd only add him and no other fish at that time.
You want corydoras? What kind? If you go for any of the dwarf/pygmy/mini corydoras you could do 5-6 (the entire school) at once, but if you do the larger panda corydoras do 3-4 at a time. Also I would only do the dwarf/pygmy/mini corydoras, or panda corydoras, or julii corydoras would be good in a 20g.
The diamond tetras get big. I have 5 in my 55 right now and am adding more in soon. I'd do cardinals or harlequin rasboras in there or something with a torpedo shaped body and do about 6-7 of them with 6-7 of the corydoras with the bettas.