[KellyL]

Hi all,
We started off with 6 molly, 2 male, 4 female. we have had them since November and all was fine and they where breeding up until about 2 weeks ago. I noticed my less dominant male was sluggish and hiding one evening (this isnt normal, even though he was less dominant) by the next day when I got home from work, he was dead.
Then I had 2 females go very, very skinny all of a sudden. One was very weak and was being blown around by the filter so I moved her to a spare tank and she died today. I was treating her with salt and melafix.
The other skinny one is getting weaker and I'm worried I will loose her too, my remaining male and two females seam fine at the moment as do the rest of my fish - even my one remaining molly fry.

Does anyone know what could be causing this? My water is testing fine with the API liquid kit, I have air in there and am doing weekly 50% water changes with gravel vac (as always)

Thanks all,

Kelly x

 

[Sakura8]

Hi KellyL. I'm sorry to hear about your mollies.

First, the females. Molly females are more sensitive than other livebearers and often, any slight shock or stress is enough to make them miscarry or drop premature fry. This can result in their deaths. It may be likely that your two females had this happen and the fry were either eaten or miscarried.

I would probably need to know a little more about your male's history of behavior but there are a number of possibilities. One is that he was simply old. It's very hard to tell the age of some store-bought fish. Another possibility is he experienced some stress during mating and that simply did him in. He could also have been suffering from some internal issue that we would have no way of knowing about without doing a necropsy.

Are you keeping your mollies in brackish water (half salt, half fresh)? Although mollies can survive in completely freshwater, they become more prone to bacterial infections and their lifespan is often shortened.

 

[KellyL]

Thanks for your answer Sakura8. I'm not sure if the females had any real stress that would cause them to miscarry although it is possible.

The male I lost went really quickly, one day he was fine the next he was slow and sluggish then he was gone! Even though he wasn't the most dominant he would still breed with the females, I dont see how he could have suffered any stress either but since I cant possibly watch them 24/7 it is possible.

The tank is 100% fresh water. I do artificially rise the PH slightly for the molly but I cant add any salt or I will kill off my cory and otto!

 

[Sakura8]

Whoops, yeah, don't want to kill the cory or oto.

My best guess then is they had an internal issue that has been brewing all this time. The worst part about internal infections or parasites is most of the time we never know they have it until it is too late.

If the two that are remaining are acting fine, I would keep an eye on them for now. If they begin to show signs of illness, it might be best to isolate them in a hospital tank with some salt and perhaps give them an antiparasite treatment. I would recommend API General Cure since the metronidazole in it will be effective against any internal parasites but it will also be somewhat effective against any internal bacterial infections.

 

[KellyL]

Im pretty sure I have some general tonic here someplace, is that the same as general cure?
I might just dose the entire tank and hope for the best.
If it is some sort of parasite/bacteria is causing this, what are the chances my other fish may be contaminated?

 

[Sakura8]

If it is a parasite or bacteria, your other fish are definitely infected. However, whether or not they pull through depends on the strength of their immune systems. Since they seem to be doing okay, I would think they are stronger than the ones who didn't make it and/or haven't been stressed by breeding or something like that.

General Tonic may help with some external parasite problems but it won't be effective if they have internal parasites or an internal bacterial infection. The active ingredient you need for this would be metronidazole and praziquantel. Are you able to get Tetra Parasite Guard in the UK? If so, that would be a better choice.

 

[KellyL]

Thanks again for your answer! I've never had fish die like this for no reason! I don't think I have ever seen tetra parasite for sale here, I will look for something with those ingredients though!
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[Sakura8]

You're welcome. It's so hard when they just up and die but there usually is a hidden cause. So many diseases and parasites kind of lurk in their system doing longterm damage, rather than suddenly and violently popping up with symptoms we can recognize.