I need aquarium suggestions and help!
So I use to have a fish tank and it was filled with your typical fish store fish and that tank is long gone now but I decided to get another tank. My previous tank was a 10 gallon and that is to small for my plans!

I was thinking a 20 or 30 gallon tank but I would like to have some money left over so if anyone knows a good site that has them cheap let me know!
I plan on putting clean pond water in the tank because normal tap water wouldn't work. There will be those aquarium stones in the bottom but I also have
small
clams (smaller than a dime) that I can get from my ponds to add and im hopping they will help clean the bottom of the tank and act as a food source for the fish and I plan on buying plants from the pet store to add and 2 snail to help with the cleaning.
Fish possibility's(3 inches in length or less)
-Catfish(channel or bullhead)
-Bluegill(sunfish)
-Pumpkinseed(sunfish)
-Bass(Large/Small mouth)
-Perch
(The catfish and perch will be harder to get) but I can catch the rest with a small hook and worm.
Other critters to help keep the tank clean and the accessional snack(for the fish)
-Small clams
-Snails
-Ghost shrimp
-Possibly a crayfish
My worries... I have 2 cats and a younger brother(Weazel) and he use to take fish out of the tank when he was younger and he would pet them and to know ones surprise they where all floating the next morning!
but I plan on keeping them then releasing them into my ponds when they out grow the tank!
Let me know what you think of the ecosystem I have came up with and am I missing anything ? and im not going to have all the fish I listed.. I plan on having 2 fish total in the tank but I would really like a couple perch but I would have to travel to get those because none of my ponds have that in them same with the catfish

but sense that's out of the questions I was thinking a bass and a pumpkinseed but 3 inches or smaller and I think they should be the same size because the bass will prolly end up eating the sunfish ?

but the easiest would be 2 sunfish.. pumpkinseed and bluegill either way those fish will get very big over time.. what do ya think ?