rdd1952 said:
You are already overstocked. A full stock in a 25 litre (about 6 or 7 gallon) is really only about 3 or maybe 4 small tetras. For the fish you have now, I would say you really need a 15 or 20 gallon tank. The general rule of thumb is 1" of adult fish per gallon(US) of water. You currently have about 22" not counting the algae eater (don't know what kind he is, some grow over a foot long).
Edited for spelling.
[snapback]909823[/snapback]
Dude 1" of fish per gallon is rediculous and nonsensical. Its a newbie rule. Once you understand why it doesnt make sense you can break it. Here's why:
10" of whitecloud minnow eat 50% as much as 10" of neon tetra
10" of neon tetra eat 20% as much as 10" of threespot gourami
10" of threespot gourami eat 50% as much or less than 10" of oscar
See where I'm going with this?
He's completely fine. I'd say he's pretty well at his stock limit, especially for a newbie, but to say that tank is only enough for a few tetras is rediculous.
25L is EASILY enough for 10 neons and a couple of otos. That's not even beginning to push if it water changes are made regularly.
TO THE GUY WHO ASKED THE QUESTION:
Yes you should ideally mix corys of the same species although you can mix from other species. Given the small size of your tank I would have said no to corys altogether. I recommend ghost shrimp or amano shrimp as a superior alternative given your space. If you insist on keeping your cory get ONE buddy for it of the same species. Also lose your lone bleeding heart tetra. Never keep a tetra alone. Not smart.
Also make sure you feed your cory bottom feeder foods. There's never enough food "just falling down".
[snapback]909921[/snapback]