redearslider.com

Is there a kind of fish that only poops like once a month?? Or barely at all?? My goldfish are just TRASHING my tank!

Keeping fish tanks clean depends on the amount of fish per tank, just like turtles. Goldfish tend to be messier than tropical fish so they require more space because of the added strain they put on the nitrogen cycle in the tank.
In a 10 gallon tank you should only have 5 inches of goldfish, but you could have 10 inches of something tropical like tetras or mollies.
Filtration is also a factor. If your filter isn't good mechanically or biologically the tank environment will suffer.

Well, I have the fish in with the turtles I have. Right now there are 2 goldfish in the tank. The are the ones that are just making the whole tank so dirty I have to clean it every week. I have a ReptoFilter, heater, bubbler, and all that kind of stuff. I am hoping that when I get the new 55 gallon tank and when the xp3 is running, the tank won't get so dirty so fast. I just kinda want to know what fish to buy that won't make a huge mess but will clean up after my turtles.

Well, goldfish certainly won't clean up after turtles. I'd suggest a smaller algae eater like an Otocinclus, they seem to be pretty aggressive with the algae. But really any fish you add will be adding waste to the tank, and will most likely be eaten. That's why you should depend on the filter to do the cleaning.

Goldfish are notorious for producing a lot of waste which, along with nutritional and parasitic issues, is one reason why they're not recommended as feeder fish in the tank. How about fewer of them in the tank?

Well, I only have 2 of them in the tank right now, I have another 2 in my other 10 gallon tank because having 4 in the turtle tank was WAY to many. My turtles don't seem to go after the goldfish, but when I get them rosy reds, the fish are eaten by the next morning. I have been wondering why the goldfish are not eaten and the reds are.