Platy Not Eating / Being Bullied

Setup:
10 gal brackish water tank (1/2 tsp aq. salt per gal.). Fully cycled tank, running for 3 months. Change 1/3 water once a week. Test Strips read just fine. 3 fake plants, rock tunnel and small cave.

Fish:
2 Molly and 2 Platy

Problem:
Sunburst Platy did great for first 2 months. Got nice and plump in the tank and ate with other fish during feeding, even seemed like the dominant platy. Recently the other platy has been harassing the out of the sunburst. Constantly chasing the sunburst around the tank, and hovering over it when it is trying to hide. Now the sunburst has not been eating and is noticeably thinner and smaller. Spends a lot of time hovering at top corner of tank behind filter or heater, seems scared to come out. All other fish are doing just fine, and no other bullying is occurring.

Please help, not sure if I should isolate the aggressive platy or the starving one.

 

I'd isolate the bully, give it a time-out. It's not fair for the bullied platy to get punished. Lol! Btw 10 gallon tank is too small for your mollies, they are huge waste producers so they need bigger tanks than a 10 gal; and test strips aren't very reliable so it would be best to get an API water test kit if you can.

 

If it is a male that is chasing around a female, there is nothing you can do about it, (in the long run) other than get another female to give the bullied one a break. I would isolate the one that has been bullied, or else chased to mate, to the point of exhaustion. I would also move the mollies to a bigger tank. Not only do they create a lot of waste, they also like to swim around a lot.

 

Have you checked the sex of your Platy? It sounds a lot like mating behavior. I accidentally end up with one female and four males I ended up rehoming the girl because she was being harassed so much. Most things I read suggested a ratio of 1 male: 2 female min for platy (1:3 is preferred).

 

Thanks for the input everyone. But how do I check the sex of the platy? We thought it was a cute mating thing at first, and the currently bullied fish was large enough to look pregnant... is it possible that there was a livebirth while we were at work and all of the fry were eaten up? Would this have any psychological impact if it were the case? Cause the bullied fish is skinny as now, and nothing is cute about the relationship anymore.

And about the mollies: Darn pet store said 10 gal was fine when I started up the tank, but I have since learned otherwise (I didnt educate myself enough at first). This is why I change 1/3 water every week so their environment is clean, just a bit small. This was my alternative to a dog for my girlfriend, but is more work than anticipated, so I am reluctant to get a larger tank. The mollies seem like they are ok... is it really torturing them to live in a 10 gal?

 

I will try to explain it, but I believe there are actual photos on the site somewhere that will show you better.... A male has a gonopodium fin that will be sticking straight back, towards the vent... with a female it will be rounder. This is the analfin that you are looking at.
It is possible that there was a birth while you were gone, they are live bearers. However, there is no psychological impact on them if they eat them, they will readily eat their young and are known to do it quite often. The impact is on the female being chased and mated with all the time. It wears them out, stresses them out and will eventually lead to death. I would get at least one other female...ideally, I'd get two. These fish will have fry aprox. every month as well....just so you know that. Most of the time they will get eaten, sometimes there are one or two that actually make it to the point where they are to big to be eaten.
Now on to the mollies... It's not "torture" necessarily....but they may not live as long either, how big are they currently? Do you have two males, a male and a female or two females....do you know that mollies are also live bearers?
Tanks can be a bit of work, ( I have 4 right now) but I've always found that the bigger the tank, the less I have to worry about, in the long run, with the water. If you had even a 20 gal. tank, you could get a 5gal bucket, siphon it out once a week and add new water back in...takes me about 15min to do that in my own 20. If I am super busy one week and don't get to it, it really isn't that big of a deal.... But with my 10 gal. tanks, if I don't get a chance to change the water, I'm starting to worry and with good reason. To me, bigger tank=less work. (unless of course you get some HUGE tank that you have to climb inside to clean)

 

Alright, thanks again for the help and suggestions. I will have to look into a larger tank. I am aware that the Mollies are live bearers, and I believe they are the same sex because none of this behavior has been present in them since the tank started.