How do I move from community to Angels? - Practical Fishkeeping

Q: I have had my 240 l tank set-up for a few years now, and my aim is to change it from a community set-up to one for Angelfish. This would be a gradual process — my plan is to replace any fish that die with Angels until eventually there are no other species, except for a few loaches and catfish. However, I was wondering if Angelfish would be compatible with my whiptail catfish and my Giant African fan shrimp. Please could you advise on this and also whether this changeover would work?

BRENDAN, VIA EMAIL

A: Neale says: While most Angels are fairly peaceful and well-behaved community fish, occasional specimens can be bullies, although in fairness, they tend to calm down in larger groups. My usual recommendation with Angels is to either keep a singleton in a peaceful community alongside dissimilar fish; a mated pair in their own tank for breeding purposes; or groups of six or more that will usually co-exist with each other provided they have sufficient space. Angels are essentially impossible to sex outside of spawning, and my guess would be that it's the sexually mature males that are the most intolerant, whether of one another, or unreceptive females, or even vaguely-similar looking species.

Bottom line, then, would be to add six or more Angels in one go, rather than trying to add them singly or in  pairs. Juveniles tend to school together more amicably than adults. Assuming the tank is mature and adequately filtered already, adding six juvenile Angels to a 240 l aquarium shouldn't be a problem.

Farmed Angels, at least, don't need especially high temperatures, which should suit whiptails such as Rineloricaria perfectly well. But if you were planning on keeping Altum angels, Pterophyllum altum, you might need to be a little more picky over tankmates, as those Angels are real hothouse flowers.

Generally speaking, Angelfish are not nippy, but the very long caudal fin rays seen on some Rineloricaria species might be pecked at. Otherwise they should largely ignore them. There's no real overlap in their ecological niches, and while both are small-scale predators, whiptails sift sand for insect larvae and other wormy foods, while Angels are adapted to feeding from the surface, consuming things like midge and mosquito larvae as well as small crustaceans and even tiny fish. In a tank with a sandy substrate, whiptails will bury themselves a bit like flounders, with only their eyes being visible, and I'd imagine that most of the time the Angels simply wouldn't even realise they're there.

Giant African fan shrimps are a bit of a wildcard. In most community tanks, you tend to find fan shrimps hanging out somewhere close to the filter outflow: a good sign they're looking for the strongest water current. So long as you're providing filter-feeder food on a regular basis, for example by using a turkey baster to direct the food at their feeding appendages, these shrimps can do well in captivity. To some extent they will forage about for organic detritus and leftover flake, but as with any aquarium resident, they shouldn't be entirely left to fend for themselves. However, these are animals from fast-flowing streams, unlike Angelfish which come from sluggish water environments, and long term, the fan shrimps are not really going to thrive in a tank tailored to the needs of Angels.