Suggestions On Fish To Help Control Breeding Molly's

Keep in mind even once split up if they've mated females can spit out 2 or 3 batches of fry before needing to mate again.

I had a Betta that was great at fry control, no survivors angelfish worked well too. Had a pair of dwarf gourami they made a dent but never got them all.

What kind of substrate? I've always liked cory's and kuhli loaches for community tanks, but neither do with gravel or other sharp substrates.

You will never be able to "control" livebearer fry with predatory fish. No matter what they are, they cannot eat this many; at least, nothing suitable for your tank sizes will handle it. And more importantly, it is not at all healthy for fish to eat other fish, not in this case. There is a real nutritional problem feeding fry to fish, and this should not be encouraged.

As Squid mentioned, female livebearers once impregnated can produce several batches of young without a male present; this is known as superfetation, and I am not certain of the number but it is several. And if you have fry present, the males can impregnated all the females long before you can even distinguish male/female via colouration, which is why livebearer breeders separate all fry within a few days.

On another issue, acquiring any fish to solve a "problem" is not a good idea, ever. These other fish have specific needs, which may or may not be provided in this particular tank. You could introduce any one or more of several problems and be worse off than you are now. Both betta and angelfish have very specific requirements, and also might not work with your other fish.

On the gravel question, provided it is fairly fine grain and not rough, it should be OK. But corys need a group, no less than five, preferably more. They are shoaling fish and this is a basic need. [This is one aspect of what I meant above by various fish having specific needs.]

Byron.

I think when it comes to storing sperm, female mollies will keep fertilizing themselves for up to 6 months or so, if you don't want fry, the best bet will be to remove all fry and females and stick with males.

or, not all livebearers are quite so prolific, or there are many more outlets for their offspring. I don't think all livebearers will store sperm for self-fertilization either.

most goodieds are endangered or extinct in the wild, you could do worse than keeping a CARES species or 2 and do your part for the fish and there will be numerous people who would love to take fry off your hand.

but, if you're going to keep the more common, ornamental livebearers then I'd suggest just keeping males.

Raphael, Asian bumblebee, or whatever relatively small yet large-mouthed catfish you can find would help.