Tetras

[KappaTheImp]

I've currently got a 15 gallon tank set up with some live plants, 2 ghost shrimp and 1 bamboo shrimp.

As far as fish go, I have two serpae tetras, and two phantom tetras. The employee at my LFS assured me that they'd school together because they're similar looking. Probably.

They don't fight or anything, and they seem to get along well, but I've never seen what schooling fish are supposed to look like. I'm content to leave them as is, if I wasn't going to make any other changes to the tank, but I'd like to go ahead and add one of my bettas, in the hopes that he'll enjoy the extra space, and hunt my thousands of nuisance snails.

Do you think it's safe to add him, or should I go ahead and get more tetras so they feel more secure? And how many do you think I can add before I'm in danger of overstocking the tank? I believe my hob filter is rated for a 20 gallon, but if necessary I can rig up an extra sponge filter for bio filtration.

[lvandert]

The general rule of tetras for schools is 6 a piece. They may school together now (I had black neons and rasboras that did that) but once their comfortable they'll split apart. Then you'll have the stress from their numbers not being high enough.

If I were in your situation I'd finish of each school and then maybe after they've all settled add your betta.

[DragonFish]

Tetras are generally rather peaceful(though some can be a tad nippy, depending)so the worry really isn't with them fighting so much as stress from lack of space or lack of a proper school. Sometimes different species will hang around each other a little if there isn't a proper school of their own species, but they won't necessarily school with other species from what I've read and experienced.

Also while Tetras don't have a HUGE bio-load...space-wise a 15 gallon is a little small for two proper schools(6 minimum per species, as lvandert said)of tetras, especially along with a betta. If I were you, I would look into upgrading if you want to keep both species in proper schools....or returning/re-homing one species if you can and building the other up to a proper size before you add in your betta.