Aggressive Molly

[feelathome]

Hi,
In the past week I have lost a tiny lamp eye tetra (literally lost it, I assume it died and was eaten) and have had a small Platty die.

Today I saw my Molly chasing a large Platty around. I thought no more of it, but about 2 hours later the Platty was almost dead and the Molly was repeatedly biting it. Each time the Platty managed to move away, it followed and continued biting it.

Is this usual behaviour? Should I get rid of the Molly, and if so, how?

can ayone advise me?

thanks

Sometimes mollies can be bastards. How big is your tank? What other fish do you have?

I had a balloon Molly that was an absolute bastard once. In a large understocked tank, she harassed other fish CONSTANTLY. She died very suddenly after about 9 months in the tank, I was quite relieved.

I guess you either rehome / euthanise her or put up with it.

Bear in mind that often the harassing fish is picking on fish that may be weak, old or ill already.

Mollies are quite big and active fish, how big is the tank? How many fish in it? Is it male or female? How many other mollies have you got - what's the gender balance like?

thanks

It is a 60l tank. I have (had) 2 tiny lamp eye tetras, 4 small platties, 2 larger platties, the molly and 4 small red tuxedo tetras.

I have now lost one of the larger platties (the first fish I ever got, about 8 months ago when I set u the tank) and one of the lamp eyes.

Got home tonight and all is well, at the moment, I was expecting to come home to some new disaster.

Can you really euthanise a healthy fish? I didn't think it would be moral, but if its attacking others, perhaps its for the best?

No, I wouldn't euthanise a healthy fish, there are plenty of other ways to deal with the problem.

I think what you are suffering from here is a simple case of overcrowding. Platies and mollies both need a larger tank than 60 litres so they have space to behave more naturally. 60 litres is only really suitable for smaller shoaling fish of 1-2".

I would think about rehoming the platies and mollies back to your local fish shop and perhaps seeing if they will swap them for some other fish.

Do you know the scientific names for the tetras you have? The only fish I know referred to as lampeye tetras are these and they are not tiny. If you have those then I'd rehome them too, they also get too large for a 60 litre tank because they should be kept in a shoal of 6+.

I've never heard of a red tuxedo tetra, if you don't know the scientific name then can you describe it?

It's a dilemma, isn't it? And it seems unfair to knowingly foist it off onto some other unsuspecting fish keeper. (Not suggesting you would do that!)
I can totally sympathise - I had a pair of American flagfish which, literally overnight, ripped my black moors' tails to ribbons in my 300 litre tank. I came down the next day to find both black moors hiding behind the filter looking like they'd been swimming through brambles - felt v guilty!

In the end I had to rehouse the Flagfish into a tank of their own - a 25 litre of so job from Pets at Home. No adequate but I was desperate. I now have them in my tropical tank with my BEAUTIFUL blue platys and black phantom tetras - I kept a close eye on them, but the are on best behaviour!

Is a separate tank an option?

no, that is not what I have, Eau. The lamp eyes are about 1.5cm long and only about 0.5 cm deep (tall ?)

and the red tuxedo plattys (Xiphophorus maculatus) are no more than 1 inch long, and the largest no more than 1.5 inches.

Oh, they are red tuxedo platys? You said tetras before, that's that mystery solved then. They are small now but they get bigger, they would need a larger tank. If you upgraded to a 3ft tank (around 90+ litres) then the mollies and platys would have more space. What's the M:F ratio?

Are these the lampeyes?

no idea what sex they are. Ive never had any fry since i got the tank in March.

sorry for my mistake getting tetras and plattys muddled up

No problem, just checking as some tetras can get pretty large!

If you've had no fry since March then it's likely you have all males. This might help you figure it out. Normally with livebearers you keep 2 or 3 females to every male to ease aggression but you do end up with a lot of fry that way.

Hi Sorry my last answer was really short, my children were waiting to start their dinner!

When I last got some fist, it was the platties. I specifically asked for that mix so I could have some babies, but since then about 6 weeks ago, nothing. I don't know if I've not left it long enough, or if the Molly is eating them all.

and yes, they are the lampeyes. I only bought them as I rescued one from the tank at work when they got evicted in favour of goldfish, I got 2 more to join it, then it was eaten last week, and I only have 2 left now.

Just done a water test, nitrate looks sky high, about 160ppm! Don't know why that would be, or how to sort it, I've never come across that before.

Crikey, that is high. Water changes are the way to get rid of high nitrAtes. Check your tap water too because the nitrAte level can be quite high in some areas. High nitrAte level is another sign of overcrowding.

Lampeyes are probably not compatible with mollies and platys. They are fine in a 60 litre tank but you'd need to increase the shoal size to 6+ because they get insecure if they are not in a large enough group.

I have read the suggestion of 1 inch of fish to 1 gallon,or 1cm per litre, or 1 fish per gallon

I have 12 fish, totalling about 20 inches, in 13 gallons (overstocked)

or
50cm of fish in 60 litres. (OK)

or
12 fish in 13 gallons (OK)

so two contradictory answers to the question "have I overstocked the tank."

How is anyone supposed to learn when there is so much different information out there.

There's probably more misinformation out there than there is information. The general guideline is 1 inch per gallon (with size of fish being the adult size) but that's a guideline. There are other guidelines as well like the tank should be 6 times the length of the fish. The best way to tell is by how the filter and tank cope with the load of fish.

NitrAte should always be below 40 ppm so it's possible that the filter can't cope. When's the last time you did a water change and how much did you do?

I did a water change last weekend, probably about 20%, but must admit I hadntt done one for about 3 weeks before that.
I'll do one tomorrow, hopefully sort out the nitrate problem, but still can't decide what to do about the Molly. It has been fine tonight, I've not noticd it attacking any of the others.

If your tap water nitrAte is higher than about 30ppm then you'll need to get some nitrAte remover (most aquatic stores sell it). NitrAte in a tank should always be below 40ppm but the lower the better. You might need to do a pretty hefty water change or maybe a couple in one week. I'd change about 60% in one go and then re-test the next day to see if another is needed. HTH.

Thanks, I knew I could rely on you for great advice.