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BadFishDaddy 06-27-2011 12:23 PM

Help with dying Mollies
Hi everyone,

I seem to have a problem keeping Mollies alive.
It got so bad that I quit buying them as I couldn't keep them alive for more than a few days. When I upgraded to my current tank I decided to give it another shot. I purchased 6 and had 4 die within a few days. One of the remaining two got tail rot (successfully treated and now doing well :-) ) Those 4 that died were due to my error of adding too many fish too quickly (I didn't know better at the time and lost about 10 fish in 3 days :oops: ).

Since I have been able to keep those 2 remaining mollies alive, I decided to give it another shot. Two days ago I bought 2 dalmatian mollies and 2 platys (as well as several more live plants). This morning when I woke up, everyone seemed fine. This afternoon, one of my dalmatian mollies had died :-(

My water chemistry was tested hours before putting them in: pH 7.4, ammonia 0, nitrIte 0, nitrAte 10, GH 11, Kh 4

Current water chemistry (just after taking the dead molly out): pH 7.4, ammonia 0.25, nitrIte 0, NitrAte 5, GH 12, KH 4.

I have always heard that mollies are sturdy fish. Any ideas as to why mine keep dying?

Thanks in advance for any information.

calebabernathy 06-27-2011 12:54 PM

how long has ur tank been set up and has it cycled cause if it hasnt and u just put fish in there u are going to loose some if it has not cycled then i would let the few fish in there cycle it and then add some more other than that u might try a difffernt store some times stores just get bad batch of fish

BadFishDaddy 06-27-2011 01:03 PM


Originally Posted by calebabernathy (Post 714041)
how long has ur tank been set up and has it cycled cause if it hasnt and u just put fish in there u are going to loose some if it has not cycled then i would let the few fish in there cycle it and then add some more other than that u might try a difffernt store some times stores just get bad batch of fish

Tank is fully cycled and numbers have been stable for months. I also can't blame the storesi get them from. I have purchased mollies from several different stores in at least three different states. I have gone to big chain stores (I.e. PetSmart, etc) to small family owned fish stores. Same results.

Thanks for the reply.
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LasColinasCichlids 06-29-2011 11:22 AM

Well, I will say this regarding blaming the stores... they could all share the same supplier (as a lot of the stores often do), and that supplier could have a bad line of them.
If they are balloon/pot belly mollies... well they have their own set of issues since they are hybrid and the ballooning is a deformation.
I do know mollies, like most livebearers, prefer hard water, even harder than your water based on your parameters you posted.
And that is a pretty big jump in ammonia for just one dead molly in a 60 gallon tank... but I assumed your tank was cycled from your water parameter postings... 0 ammonia and nitrite with 10 nitrate is usually a good indicator for me.
It could just be a fluke. Mollies, or any fish any more, arent as hardy as they use to be due to so much over-breeding. Then again, it could be the tankmates. Serpae tetra are nippy creatures, and unless in a very large group of 9-12+, they stay pretty nasty with their nipping inside and outside of their group.
Wish I could tell you more, or have the answer for you.

BadFishDaddy 06-29-2011 11:29 AM

Thanks again, I appreciate the info.

mattfishgeek 06-29-2011 01:10 PM

just curious but before the mollies are dying then are they feeding and swimming correctly such as not shimmying?

BadFishDaddy 06-29-2011 01:35 PM

The most recent one looked fine in the morning and was dead in the afternoon. The previous loss of mollies, was due to not having a cycled tank, so their behavior doesn't really count. Prior to that it's been years since I have tried to raise them and I don't remember their behavior.

Byron 07-02-2011 05:59 PM

I readily see two possibilities.

First, mollies are not "hardy," quite the opposite. They are frequently selected to begin with, and almost always die. They cannot tolerate any ammonia, so the tank must be well established before molly should be introduced. I have this from a professional molly breeder in Florida. Even if they seem to get through the beginning stage, the ammonia at levels above 0.1 will seriously affect the fish internally, and down the road it will be obvious.

Assuming water was not the issue, I think Amanda hit on what likely was. The Serpae Tetra. This is not a fish for a community tank with any sedate fish such as molly. It is quite possible that the Serpae hounded the molly to death. They don't need to physically attack it, though Serpae are notorious for nipping fins; just being in the same tank will cause considerable stress for fish that are sedate and can't tolerate such threats. Fish send out chemical signals, pheromones, that other fish read. Highly stressful.

Serpae should be in larger groups to reduce their natural aggression, at minimum 8 but preferably 12 or more; and that size a group will be fine alone in a 30g tank; in larger tanks that sized group can manage with other robust fish, but nothing sedate or with long fins which will be too much of a temptation.


BadFishDaddy 07-02-2011 09:11 PM

Hi Byron,

Things are now starting to make sense. My years of being unable to keep mollies probably had something to due with the ammonia as I never checked that previously and did not do water changes like I should have.

As for my Serape Tetras, I have a question or two. I currently have four. They were recommended as good fish in my tank (no mollies at that time). They don't seem to be aggressive and sometimes even appear to school with my platys. I have never seen them nip at any other fish. For the most part they stay together and don't seem to bother others. Do you think I am OK keeping them with my current tank? The three mollies I still have seem OK, two of them have been around for several months and aren't showing any signs of stress. If I keep them, should I get more of them to help prevent aggression, or would it be better to take them back to the store(this would make me sad, but not as sad as having my fish dye)?

Thanks again for the advice.


LasColinasCichlids 07-02-2011 09:19 PM

At one point I had 6 Serpae Tetra in my 29g with 6 brilliant rasbora, an albino rainbow shark and some cories. For the first couple of months those tetras gave me no issues. Then, I assume after they felt comfortable, they decided to start nipping at each other a lot... then they would try try to irritate the shark. They never really messed with the rasbora as these fish were a tight school and if they werent minding their business they were very ground standing. But I drew the line when the serpae started to nip at the poor harmless cories (albinos-bronze)!!

If it were me, I would return them. They are defiantly a fish that does best in a large group, and even then only with carefully selected tankmates. Your tank size compared to stocking level is probably why you havent yet had the issues with them, but in due time they will arise.

If the serpae were to school with any fish, I would have thought the lemon tetra to be their first choice. That is interesting.

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