Goldfish tank mates?

[Tatianna]

So please don't jump off my screen yelling, but I am checking here because I am getting conflicting answers. While the majority are saying no.....my local fish keeper does this with no problems (or so he says).
Can goldfish and betas be kept in the same tank? When we go to our local fish store (small one person owned shop) he has some in a tank together some separate. He tells us that he has done this for years and never had a problem. Now I know that Betas are tropical and goldfish are not, but how is he able to keep the fish in the same tank if it can't be done?
I have a 15 gallon tank with one young fantail goldfish right now and would like to add another fish of some kind without jumping up to my 20 gallon tank because someone (from another store, a larger retail store next town over) is telling us our goldfish's strange behavior (laying on the bottom of the tank sometimes) might be because the fish is 'lonely'.

If I can't put a beta in there is there another fish that would be compatible with a goldfish? So I will have another option instead of buying an even bigger tank and adding a second goldfish?

I should also add that I do have a small isolation tank that would be perfect for a beta so I will probably get one either way eventually, but mostly I am looking for a compatible goldfish tank mate recommendation....if my local fish keeper says betas and goldfish are good together and they truly are not I am not sure I could trust his word on another tankmate...

 

[OrangeCones]

Keeping coldwater fish and tropical fish is not impossible, but not good conditions for either.

If you are wanting a 'companion' for the gold fish, I would try white cloud minnows. They stay small and cold-water is fine for them.

The local fish shop owner may have or currently be keeping those fish together in the same tank, but its not ideal for either. Think if it this way:

Can I build an exhibit and put a toucan and a penguin in the same space?

Probably.

Will it be a healthy place for them both?

Not likely.

And just because the shop owner is doing it, no way to know how long the fish involved are living. Stress will kill the fish at an earlier age than what should be a 'normal' lifespan, as well as make them susceptible to diseases they would normally be able to resist getting.

 

[FreshyFresh]

Yep, white cloud minnows or even some zebra danios can do OK in cold water. Really though, 15g is enough for one fancy goldfish.

Like I should be one to talk... I've currently got a comet in a 20 long.