Help with Mollie Fish !



Can anyone help me, I have just bought 75l tank, had it a few weeks now and have 4 ( 2 black, 2 silver - don't which are male and female!!!) mollies in and 2 honey gourmani, one of my silver mollies is quite aggressive and chases the 2 other black mollies around, when I take the silver aggressive one out the 2 black ones are fine and start showing all their fins which hasn't happened before, just wondering if anyone knows why they would do this ???

Any help would be really appreciated !

Thanks  ??? ??? ???


um how many gallons is 75 liters?? heheh...and is the tank cycled?
to help you sex your mollys, males have a tube-shaped analfin, and females have a normal one. The analfin is the fin on the bottom closest to the tail.


oh nm about the gallons/liters thing I used the calculator on fishlore and its about 20 gallons correct?


I think shes a female ( the one chasing the 2 black ones around ) she seams very aggressive to wards the others. My 2 black mollies seam to hide a lot and have closed fins.  she doesn't attack any other fish? and doesn't seam to be bothered about the other silver one who is generally bigger and has a massive tail an long fins under its body.

are my other black mollies scared or are they ill. I did change about 25% of the water the other day hoping this might of solved the problem.......... BUT NO.   She stills chases the other black mollies around.

Just before I removed the silver Mollie (the aggressive one) to see if the other black mollies were any better without her around.   The 2 black mollies started swimming more freely and showing there fins.  I only removed her for about 5 Min's but once I put her back in the tank she started chasing them again like nothing had happend.

what should I do now.... PLEASE HELP ??? ??? ???


I think its about 16.66 gallons. I'v just had the calculator out 2.

I belive 1 gallon = about 4.5 Litres

so 75L / 4.5G = 16.6666

That's has close has I can get lol.


try the caluclator on, that should be a bit more accurate. So is the tank cycled? Do you treat the water before adding it?


Estimated you have 20 gallon it comes out to like 19.8


yep, that's what I found, I guess its not 4.5 L per Gal?? I'll stick with the auto-changers lol...


even better I have a 20G tank. What do you mean is it cycled? do you mean a filter etc.

Yeah I have a filter, heater and the temperature reads 26c. Yeah the water is treated and warmed before I introduce it back into the tank. I change about 18litres (25%) a week and feed them twice aday.


cycled--could you read the article (on fishlore) on the NItrogen Cycle? This will help you a lot. I'm guessing your tank isn't cycled then.


seems like you might be changing your water too much? Read that article great one! You should only be changing the water once a month! She might be aggresive because of all the water changes. They recommended to me having 2 females and 1 male because of the dominance. If you do have 2 males and one female, just try and get 2 more females and see how she acts, cut your changing the water down to once every month and do a 50 % water change...hope this helps! Good luck! She might just be aggressive because the males will gang up on her at some time and she is trying to show them who is boss! You go girl! ;D


Once a month may be too infrequent. More like once a week would seem to be the norm and only about 20%-25% to keep things in check. However, if their tank hasn't cycled, daily water changes would be recommended until the cycle completes itself. Warmer weather is approaching as well, which also means time to spawn.......Sometimes, spring fever kicks in and nature takes over. Not entirely unheard of......or out of the realm of possibilities.


thanks for all ur help, just have one more little question.....

recently most of my mollies have started sticking out these little fins - 2 sets of them one at the top end of their body and the ones under neath a bit further down their body out loads, does any one know whey they are doing this ???

thanks again !!!


Um...woodsplace 1, I don't know where you heard that, but once a month is not enough. You need to do 20 or 25 % water changes once a week in order to maintain good water quality. Weekly changes will not stress your fish provided the water is the same as in the tank, but poor water quality due to lack of changes will.
naomi_5, what fins are you talking about?? Look at an anatomy chart in a fish book to see what they are.


Fish will extend their fins when they are feeling good. They have analfins that extend when they swim or sometimes to help hold them stationary.

Dorsal fins standing tall is a good sign of a healthy fish.


Not for all fish -- for some it means stressed/scared

I'm not sure if you were talking specifically for a molly or not


I was talking in general.....Stressed and unhealthy fish are usually noted with sagging dorsal fins or clamped fins along with faded coloring....Typically fish with fins standing fairly tall and spread, are signs of health, alert and sometimes confrontational or in defense. They'll sometimes spread their fins to show their size as if to say 'See how big I am? Now stay away....'

I see it all the time with game fish.


thanks 0morrokh...didn't know that...getting info from the local aquarium store about changing water every 3-4 weeks, but they are saying a 50 % at least water change...they never said anything about 20-25 % water change every week...YIKES...I wonder if that is why my molly hasn't delivered her fry yet because of the water quality...all has tested good except my Ph has been high but I did get some Ph down and will test again next week...thanks for the update though, appreciate it!


One reason your pH is elevated could be because of the water quality. Fish waste will effect your pH and if left to build up over time it could cause your pH to fluctuate. I would do a water test and change the water before adding any pH buffers. Test the water again in a couple of days to see if the pH has stabilized.

Do you know what your water pH is out of the tap after gassing out? That would give you a pretty good benchmark.


ph coming down...thanks to all your advice...glad I read this and left some advice, then got some of my own...that is what I like about this site...learn something new everyday! appreciate it!



since my first post my whit mollie fish has just had babies - we didnt even know she was pregant just seemed a bit bloated but not acting different at all !!

I have about 10 in my tank at the moment and have tok the other fish out, my mum is in the middle of making a homemade net for them but I don't know what to feed them or if I should keep the mother in !!

thank you all !!!


sure wish I could help you naomi...I am in the same delimma as well, my little molly is preg and about to deliver her fry. I have just as many questions as you do. I am pretty sure you will need to keep the baby away from all the adult fish until they can't fit into any of the adult's mouths...(apparently they will eat their own, ironic) you should put the baby in a breeder net or box and feed it very small amounts of fish food, (crumble up the food you have and feed it about 3 times /day) she will prob have more babies so keep an eye out, there might be some hiding out in plants if you have I said, watch out for the other fish, they do eat the babies :'(
keep up the good work and congrats, can't wait until my little one has her own little ones as well!


I know I was so excited only had them for a month !

i've had to put them away from them til I get a netbreader tomorrow - wasn't expecting it at all !!

wish me luck.... really going to need it !

wish I could help 2 !


The easiest way to feed your fry is to take a zip lock bag and some flake food. Put a small amt. of flake food into the bag and crush it into a powder. Then, get a wooden toothpick and dip it into the water. Dry it lightly so that the tip is still moist. Dip the moist end of the toothpick into the powder and then into the water. This will dispense just enough food for the fry. Do this 2-3 times daily. If you can't do it 3 times, twice will do. They won't starve.

As they get a little bigger, you don't have to crush the food as finely.

Have fun and good luck.


NaomI 15 here are some articles to read that will clear up a lot of your questions.

Let us know if you need anything.


BTW 1 US gallon = 3.78L
1 UK gallon = 4.65L

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