Question on fish compatability....

When I first got my tank, I had bought a few of those red and blue neon fish (not sure of the name), they died. I cleaned the water out, let the filter run in the tank for awhile, and tried again. I got A goldfish and 2 rosies, about 1$, because I didn't want to spend to much money on another failure. I've learned more now and I've had the tank for a year. Not even sure how many gallons the tank is, it's more than 10 I think, do they make 15 gallon tanks(got the tank from a friend, no one knows how big).

Well after a year I've added 2 small mollies and 2 fire tetras, and everything is going fine. Anyways I want to add some more of those neon blue and red fish in. Will they work ok with the rosies and other fish? The goldfish is also gone, gave it away.

Rosies are those typical feeder fish as well if anyone needs to know. Thanks.

It's a hexagon shape tank so I'm not sure how I would measure that out. Yea, I didn't know much about fish tanks when I got it so I went with the learn as I go way of thinking for it.

It's about 44 inches around and 16 inches high.

I also have a painted glass fish and one normal tetra around which I forgot about. So that would put me over my limit then.

What does bio-load do anyways. The fish seem perfectly fine in my tank.

For some reason I think my tank is bigger than 8 gallons, but the measurements would say wrong. I used a 5 gallon bucket to fill it, I think it was 5 anyways, and it didn't even fill it halfway.

Woah I'm just forgetting all kinds of stuff....

2 fire tetras
a normal tetra (I think that's what it is)
a painted glass fish
2 rosies
a pleco
and 3 unknown school fish
2 mollies

All about an inch in size, and have been living in my tank for about a year and all seem happy and lively. I even had a Goldfish in there who was about 3-4 inches and everything was fine then(just got rid of him a few days ago). So, assuming it's an 8 gallon tank, I should be bio-overloading then right?

Don't flip out on me either please, I bought all these fish before I knew of any kind of fish tank stuff. So yea, newbie to fish tanks basically. Good to know now though, I won't buy anymore fish right now.

But for future reference, would rosies work with the neons?

Well I guess I'll have to skip in the neons then, I'm not going to kill the two rosies off just to get rid of them. Walmart isn't going to take them back or anything. Wish I could get rid of them though.