I've got a stupid question.

This is referring to the same general species.

Sookielee said:

This is referring to the same general species.

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Nods in agreement - a "group", especially as mentioned in a specific profile, is all the same species.

Sooo, like scissortail rasbora can be with any type of rasbora, or just scissortail?
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T4V3N said:

Sooo, like scissortail rasbora can be with any type of rasbora, or just scissortail?
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It usually means just scissortail. There are different variations of the same species that will school together. For example Zebra Danios (golden, regular, long fin, glow fish) and Tigar Barbs (regular, green, albino).

Ohh, okay. Got it. What about cory catfishes?
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T4V3N said:

Ohh, okay. Got it. What about cory catfishes?
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Yep, they'll school together

And by the way, no question is ever stupid, if you don't ask, you don't learn ;-)

Cool. Thanks.

Now I've got another question... Now I have a upside-down catfish who keeps hiding, even when I turn off the lights and it's dark. It doesn't budge from where it's hiding(behind the filter). It was hiding within a space inside the filter, which was safe but highly agitating since I couldn't see it nor know if it's eating food or not. I'm going to be moving it to a 20 gallon once I buy one and have a exterior filter so it won't be able to hide. I even bought a cave for it, it went in, but still didn't like it. It keeps going back to the filter. Any thoughts on why it keeps hiding and not swimming about when it's dark?

Cory cats will school together, but a lot of people believe that you should have at least 5 of one species before adding another species.

Agree. And on the upside down catfish question, it is lonely. As it mentions in the profile, this fish is best with 3-4.

Others answered the group question, but this is very important. Shoaling fish live in very large groups of their own species. They must have a group of that species or they will almost certainly be stressed, and that cause poor health and brings on disease. Almost all fish disease is initially due to stress, so avoiding it is always best.

There can be several reasons why a particular fish needs a group. Security is obviously one; the more fish there are together, the safer they will feel. But many have social interactions, or perhaps a "pecking order" within the group, and this is an essential part of the fish's character.

Studies have now proven conclusively that shoaling fish that are not kept in minimal groupings will display increased aggression, and this cause yet more stress.

Byron.