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TROPICAL How do I stop these fish breeding?
I have a 450-litre planted community tank. Is there a way to stop my mollies having babies? I love the fish, but I must admit that I regret ever introducing them to this tank.
IAN BIBBINS
NEALE REPLIES: Eggs and fry are often consumed by other fish and, in the absence of zooplankton, many newly hatched fry will starve to death without regular offerings of suitably small alternatives, such as brine shrimp nauplii. But once you start talking about animals with relatively large offspring that are able to consume algae and aquarium detritus, such as snails, cherry shrimps, and most livebearers, things are very different. They are big enough—or mobile enough—to avoid casual predators, and opportunistic enough to thrive on whatever food they can find in the tank. The end result is that lots of babies survive to adulthood.
This is a common problem with livebearers such as mollies, platies and guppies, and some people keep just a single sex group of them to avoid breeding. Obviously, a group of males isn’t going to produce fry, and while females can produce batches of fry even after the males have been removed, they can’t do so indefinitely. My understanding is that the record for superfetation, as this is called, among poecilid livebearers is six months in the case of Heterandria formosa, so with any luck, your female mollies will be ‘empty’ within a few months of removing the males.
But be sure to remove juvenile males as well: male mollies mature surprisingly quickly - long before they reach adult size.
TROPICAL How should I re-stock this tank?
I have a planted Fluval Flex 123-litre aquarium. My fish stock has gradually diminished through old age, and I now only have two otos, which are around four years old, and some cherry shrimp. I’ve been contemplating adding a shoal of galaxy rasbora and asian rummynoses, or black phantoms and either ember tetras or dwarf pencilfish.
Corys or whiptail catfish have also been shortlisted, although I’m not sure whether I have enough floor space for these. I would like a dwarf cichlid of sorts, but I’d imagine that will seriously impact on the shrimp and my water may be a bit on the hard side at 17-18°dH for t
