How can I stop my Platies pestering my Angels?
I’ve got a selection of fish in my 200l/44 gal tank who have been absolutely fine together, including three Angelfish that I’ve had for four years.
Four weeks ago I added 10 Platies to the tank and they seemed to get along with the Angels at first, but then they started to attack all three – pecking at them and chasing them constantly. One of the Angelfish has now died and the Platies are continuing to peck the other two.
Can you offer any advice as to why this is happening and how I can stop the Platies’ aggressive behaviour? When I purchased them, I was told they would be fine with my Angelfish. JULIE, BY EMAIL
NEALE SAYS: It’s debatable whether Angelfish produce the same nutritious mucus on their flanks as Discus, the idea being that Discus have to do so because there is otherwise so little plankton in their environment that their offspring run the risk of starving to death without such supplemental nutrition. Angelfish, generally coming from more productive waters, probably don’t need this particular adaptation, whatever their other similarities. But, even so, Angels do seem to be vulnerable to attacks by other fish pecking at their sides, presumably nibbling away at the mucus on their flanks.
The usual situation is where the Angelfish develops bloody sores or missing scales on their flanks. Sometimes, aggression between the Angels gets things started, with them pecking at one another and opening up a sore that becomes an easier target than otherwise intact skin. It can also be the case that small suckermouth catfish – most commonly, Otocinclus – latch onto the Angels and scrape away at them, just as if they were feeding on algae.
Either way, the sores become worse over time, and the weaker the Angelfish, the more vulnerable it is to opportunistic attacks by tankmates keen to make a meal out of their skin, blood or mucus.
I’ve not seen Platies do this, but I have seen Mollies ‘having a go’ at Angelfish in this way, so it’s possible that this is the situation here.
As to whether this behaviour by the Platies can be reduced or stopped, one explanation for why Platies might be doing this, and indeed other herbivorous fish such as Mollies and
Otocinclus, is simple hunger. Such fish evolved to feed more or less constantly on algae and soft plant material, and without a source of high-fibre food to make them feel full, they’re driven to find alternative sources of nutrition.
Throw a few slices of courgette or squashed cooked peas in your tank to see if your Platies will feed on these instead of your Angels. Algae pellets of the sort used to feed plecs are good too, but being more protein-rich they’re going to put a heavier strain on your filter so be careful with those. Fresh or cooked greens contain little to no protein, so even in large amounts they won’t do much to affect water quality, which is helpful.
Otherwise, Platies are normally good fish in community tanks, so what you report is a bit unusual. Sometimes they can be aggressive towards one another, but they usually ignore dissimilar species. Nonetheless, if augmenting their diet doesn’t dissuade your Platies from taking potshots at your Angels, I fear you will have to rehome them.
Throw a few slices of courgette or squashed cooked peas in your tank
Platies eat more veg than most people think.
Otocinclus eat high-fibre food almost constantly.