Originally Posted by Salacious
Now how about that stocking rule?
Yea no the 1g/1fish crap... toss that out of the door.
There's a few things you wanna keep in mind when stocking a tank:
1) Different fish like different area's in the tank, eg top, middle or bottom
If you get 50 fish that all occupy the top naturally - You will have a problem; if you get 50 fish that some live up top, some in the middle and some on the bottom (like your cory) then you won't have a problem
2) If you have a 20g with 0 plants I'd suggest less fish; if you have a heavily planted 20g you can allow more fish as they can hide and get out of one another's way if they'd like to
3) Chose fish that are similar in behavior. Like your Cardinals are peaceful fish, don't mix these with a active or even aggressive fish, that'll just stress them out and make them die quick.
Last but not least, obviously you wanna add fish that'll thrive in your water, in your case judging from the Cardinals I assume you have soft acidic water - So chose fish that like that
You started with Tetra & Cory- Do you wanna keep stocking various Tetra schools or WHAT kinda fish do you have in mind?
There's Hachets that would go along and pref the upper part of the tank. I'd def suggest to stock the Cory to a group of at least 8, if they're less then that they tent to be skiddish and not really develop this real awesome to watch group behavior.
Gosh since you're assuming having the same water then me I could name a ton fish now...but like I said, keep the 3 ideas above in mind and then its up to what YOU like. Shop the store see what 'looks' good to you, write down names and do reseach at home or ask on here how well they'll fit in the tank (pls don't listen to the sales guys at stores, more often then not they have NO IDEA and are just THAT a SALES person).