Platy Fish Dying?

Question

This is our second time owning a fish tank.  Our first fish tank was a 25 gallon with two goldfish.  That was many years ago.  Both fish lived for years.  We decided to get a 15 gallon fish tank kit with 5 platies... all males (employee from petco stated).  I don't want them to breed.  Anyway, they are all about .5 to 1 inch.

The largest platy keeps headbutting the other fish which made them all hide, except for one.  He also headbutts the aquarium while looking at his own reflection.  I feed them tropical fish flakes 3 times a day since that's what was stated for juveniles.  Then it will be 2 times for adults.  We have a filter and a water heater since they are tropical fish.  We added a water conditioner and beneficial bacteria to the tank.  There is fake plants, 2 coral reef decorations for the platies to hide, a bubbler with stone, and Seachem Flourite Black Clay Gravel.

I don't know what else to do?!  After the 3rd day of having them, 2 out of 5 died.  One was inside the coral reef and the other was behind it. I don't know if it's the bully who is killing them or something in the tank.  Oh, and before we put the fish inside, we waited 3 weeks for the tank to cycle.  Any fish experts who can help?  Here is a pic of the tank.  Maybe you can see what is wrong.

noselessman · Accepted Answer

Was your tank cycled? 
Did you carefully acclimate them? 
I dont buy fish if there are dead fish in the tank.  But I still can not guess what is going wrong.  Bad stock?

Platies are livebearers.  The males are always redy to go, and even when noe females are around, they can act territorial, waiting for when a female does show up.  Your tank does not have places were territories can be established.  You can try hang some silk plants upside down on somthing that floats like a pool noodle to create a sense of sections.

WhstlRobn · Answer

It sounds like you have a bully fish. They can kill the other fish by ramming or just chasing them which is stressful. I've raised livebearing fish for many years, (50+) mainly Platies. I found that 'runt's often get bullied by a large fish. Male Platies will often spar with each other but it's usually harmless.

If one is too much you need to provide either hiding places to break the line of sight or remove the bully. Don't be surprised to find another Platy become Tank Boss, but he may be nicer about it. I've also noted that bully males use a lot of energy and don't live as long as the others. They eventually end up hovering in a corner in poor health. They can be humanely put to sleep with club soda (room temperature) in a jar if you don't want to leave the fish to die in the tank.

I have a video on O'Fishely Channel on Youtube if you can watch it: it shows natural Platy behavior where the males spar. No fish was harmed by this. They only did this once in a while. Water changes would bring it on with mating interest. You can also try lowering the water temperature gradually over a week to 75-76 degrees to reduce aggression in these fish. They don't mind the cooler water and will live longer.

I also found that the Hamburg Black Platy/Swordtail hybrids had the most aggressive males.

Platy Fish Dying?

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