Abnormally Aggressive Black Velvet Molly

Hi all,

I have had a 36gal community tank for the better part of a year. At first I had a male guppy, two male golden panda lyretail mollys, 2 male and 4 female platys, and one male and one female black velvet molly.

Over time it became obvious that the male black velvet was bullying the female. It got so bad that she had popeye from running into things trying to get away from him and her fins and tail were almost completely ripped off. I eventually removed her and she recovered completely in a medicine tank, and now she is healthy again thankfully. I ended up getting two more black velvet females to help with the chasing and so far none of them are being singled out, however his chasing of them is near-constant. Every time i look at the tank, day or night he is courting them and chasing them around.

Recently one of my lyretails died from unrelated reasons, and i only have the one left. Now its come to the point where my black velvet is chasing my lyretail around and bullying him into the corners. I assume this is territorial behavior but I’ve kept many mollys over the years and the chasing hasnt been this bad before. Does this have anything to do with my other male lyretail dying? I want to breed the golden pandas anyways, so if I get more of them, will the black velvet chill out a bit?

Koenator said:

Hi all,

I have had a 36gal community tank for the better part of a year. At first I had a male guppy, two male golden panda lyretail mollys, 2 male and 4 female platys, and one male and one female black velvet molly.

Over time it became obvious that the male black velvet was bullying the female. It got so bad that she had popeye from running into things trying to get away from him and her fins and tail were almost completely ripped off. I eventually removed her and she recovered completely in a medicine tank, and now she is healthy again thankfully. I ended up getting two more black velvet females to help with the chasing and so far none of them are being singled out, however his chasing of them is near-constant. Every time i look at the tank, day or night he is courting them and chasing them around.

Recently one of my lyretails died from unrelated reasons, and i only have the one left. Now its come to the point where my black velvet is chasing my lyretail around and bullying him into the corners. I assume this is territorial behavior but I’ve kept many mollys over the years and the chasing hasnt been this bad before. Does this have anything to do with my other male lyretail dying? I want to breed the golden pandas anyways, so if I get more of them, will the black velvet chill out a bit?

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Do you have a pic of your tank? Maybe try if possible to move or add stuff to it to break up the territory a little?

WetPetMum said:

Do you have a pic of your tank? Maybe try if possible to move or add stuff to it to break up the territory a little?

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here is the tank, i have some large rocks that I thought would help but as you can see all my fish tend to congregate at the top of the water column...

Yeah, you need some tall plants to block up lines of sight and provide hiding places. Some floating plants would be helpful too, and make the fish feel more secure. Aim for plants that will cover the entire height of the tank, like fast growing stem plants.

AdoraBelle Dearheart said:

Yeah, you need some tall plants to block up lines of sight and provide hiding places. Some floating plants would be helpful too, and make the fish feel more secure. Aim for plants that will cover the entire height of the tank, like fast growing stem plants.

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I’m working on that, however my plants have been slow growing or just die. Maybe a topic for another thread, but thank you I will keep trying!

Koenator said:

I’m working on that, however my plants have been slow growing or just die. Maybe a topic for another thread, but thank you I will keep trying!

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Ah, live plants can be tricky when you're new to it!
But basically, the whole top 3/4ths of the tank is wide open clear space. The fish can't help but see each other, can't hide, and the stress of feeling so exposed is also going to increase erratic/aggressive behaviour.

If you go out and buy some big bunches of cheap stem plants like anacharis, hornwort, water sprite, guppy grass or water wisteria, they're inexpensive and fast growing, and can be thrown in and left to float in a dense bunch at the top of the tank. As it grows, you can plant some stems so they reach up and provide cover for the full height of the tank. Once fish aren't directly in each other's eyeline as much, it's easier for the bully to get distracted and forget to chase, for the victim to hide, and the fish to feel more relaxed since they don't feel wide open and exposed to predators. Floating plants like frogbit, duckweed, salvinia etc provide surface cover so they feel safer from predators above (they don't know there aren't any!)

Alternatively, you could see what you can do with some tall driftwood, tall fake decor, and some fake plants. They can even be suction cupped to the sides of the tank if necessary. But all of that wide open space isn't good for most fish, but especially if you have male and females trying to breed, then they're going to chase each other. Occasionally you'll get a male that's a relentless bully, but they're rare, like one in every 2-300 rare, but open tanks with no hiding spaces are a common cause for this sort of problem.

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Mollies can sometimes become territorial. But I don't think that that's the case. He's showing his dominance. If you'd like to keep him in there, I'd recommend to get more hiding places for the others. If I look at your tank, there's sufficient space but there's no where to hide for the other fish. Or just replace this male.

Koenator said:

I’m working on that, however my plants have been slow growing or just die. Maybe a topic for another thread, but thank you I will keep trying!

Click to expand...

A quick solution could be to plant an already developed bamboo shoot/stalk. I've had a few on both my tanks for months now and they live just fine. The leaves are wide and large, create good hiding/line of sight lines if needed.