How do I hatch and rear Angels?

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Neale Monks gives his advice to a reader who suspects his Angels are eating their eggs, and would like to know whether he should remove the eggs to try and give them a chance.

Q) About a year ago I bought a secondhand 150cm tank as a complete set-up with fish. It contained Congo tetras, Mascara and Torpedo barbs. I also had a much smaller aquarium with two Angelfish, and after much deliberating decided to put them in the larger tank where they have been for about five months. The Angels have laid eggs six times now, but on average after three days they have disappeared, and I think the Angels are eating them. The first couple of times I thought it was probably because they were new parents but I’m now wondering if I should remove the eggs and try and give them a chance. If I decide to do this, what’s required, and at what point should I remove the eggs?

DAVID POUTON, VIA EMAIL

A) NEALE MONKS SAYS: This is a very common problem with farmed Angelfish. All cichlids will eat their eggs if they feel their present environment isn’t safe enough for their fry to survive, so by eating the eggs they recycle the energy spent laying them, ready for use whenever conditions improve.

This sort of behaviour, while strange to us, makes good sense in terms of evolutionary biology. Over time, natural selection works against parents who waste their time and energy looking after eggs that then hatch into fry that either starve, get eaten by predators, or in some other way fail to survive. Such parents aren’t likely to have the energy to lay eggs and rear fry once conditions become suitable, and so their genes are selected against, whereas those parents who do bide their time, only bothering with eggs when conditions are more suitable, will have their genes passed on to the next generation of Angelfish.

So far, so good. Under aquarium conditions, and especially on farms, it’s common for humans to remove the eggs once spawning has finished. This has a number of benefits, not least of which is that the parents will quickly lay another batch of eggs once ‘conditioned’ with a good diet and suitable water.

Fish breeders will keep pulling out each batch of eggs, the parents will keep laying new batches, and a sort of production line of baby Angelfish develops, maximising profitability.

The problem here is that because the parents don’t protect the eggs or rear the fry, there’s no selection in favour of these talents. Over the dozens (if not hundreds) of generations since Angels were first bred in captivity, we’ve ended up with all sorts of breeds and varieties, but not necessarily particularly intelligent or skilful parents.

As a result many breeders end up ‘pulling’ the eggs from the parents at some point. The fry are quite large and easy to rear, though without the parents you will need ensure unfertilised eggs don’t turn mouldy and infect the healthy eggs by using something like methylene blue in the rearing tank. It takes about a week or so for the eggs to hatch, and another day or two while the fry pass through the non-feeding ‘wriggler’ stage.

Once mobile, they will consume brine shrimp nauplii readily, and after a couple of days of this, will happily take commercial fry foods like Hikari First Bites. Indeed, some aquarists skip the brine shrimp nauplii stage altogether and rely on commercial foods, but this doesn’t always work. The fry grow quite quickly, and will be big enough to sell within about three months.

It’s really down to whether you want to rear a sizeable batch of Angelfish fry (in which case rear the eggs yourself) or if you’re are happy to let nature takes its course in their present tank, and if some fry survive, that’s a bonus.