How can I stop my Platies pes­ter­ing my An­gels?

Practical Fishkeeping (UK) - - Fishkeeping Answers -

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.

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