I currently have an empty 4 gallon (I think) with an underhood filter that is sitting empty. What should I fill it with? Obviously not goldies... I'm thinking either another betta or a few tetras. Anyone have a different idea, or an opinion?

well a guppy if u want lots of babies lol..or those cool glowing fish that are really small i had 10 of those in a 7 gallon! they have stripes that make them glow! and they are cheap i got like 10 for 5$

I think either 1 betta, or maybe if you seperate the tank in 2 you can keep two bettas. I wouldn't get a guppy mainly because they breed alot.
Neons sound ok aswell. You Could get a betta and add a few tetras (that is if your betta isn't too agressive)

Good luck

-Alex

Do you have a heater? I wouldn't recommend tetras. All tetras should be kept in a MINIMUM school of 6. Which your tank is not large enough for.

What about some white cloud mountain minnows? A school of 6 would be pushing it in a 4g, but with good tank management you could pull it off. They don't need a heater either.

If you have a heater:

1 betta and 2 african dwarf frogs
OR
(split) 2 bettas
OR
2 female bettas(lots of hiding places or the weaker one will be stressed)
OR
A pair of dwarf gouramis. They are lovely little fish and would do quite well in a 4g.
OR
2 male guppies and some ghost shrimp
OR
4 male endlers and some ghost shrimp

The tank is too small for anything else. Let us know what you decide.

I forgot my personal favorite. If you make it a brakish water tank you could have a pair of bumblebee gobies. I have a pair in a 6g and they are just the funniest things ever! Soooooo cute.
Just make sure it IS brakish. A lot of people will tell you they are a freshwater fish. They are not!!! No more then mollies are. Yet they still sell as such. Such a shame...

Thanks Raven ! I'm sure that with all your suggestions I'll manage to find something that appeals to me!

um, just to let you know - you need 8-10 gals for dwarf gouramis!

I just looked up the bumblebee gobies, and I think I'm in love! They are SOOOOO cute! Now I'm all giddy at the possibility of new fishies!

lol!! b-b gobies are very cute!!
let us know on what you decide!!!

I've had a pair of dwarf gouramis in a 6g for 3 years. No probs.
It's not the best way to keep them but it can be done with proper maintenance. You're right though Tinkerbell, thinking it through, a 4g is pushing it. The minimum tank size for a pair is 5g.
I was just trying to think of small fish that do well in smaller tanks. Bigger is always better!! Cheers, can't wait to hear what you decide.
If you do decide on b-bee gobies, do yourself a favour and research the heck out of brakish water fish. It's makes it much easier later on. Again a 10g is better, but with proper care, it can be done.

My fav freshwater fish site: www.badmanstropicalfish.com

Most knowlwdgeable people on the planet + they don't pull any punches. They tell you what is best for the fish, not what's best for you.

Uuuhhhhhhh. I mean they are nothing compared to you guys!!! Please don't kick me out.... C ya.