Thank you for your help.

I recently had a problem with aggressive guppies. We have (had) 6 guppies, 3 pairs. We're not pro's and don't even know their types, but two were yellow, two were red/orange and two were smaller & blue. All very pretty and active. We also have 6 Tetras in the sparesely planted 80L (20Gal) tank with an overkill filter. No population pressure here!

Both Blues were agro. Not full-on psycho's but constantly bugging the Yellows and bitting at their bottom fins and possibly anus. One of the Blues began this behaviour immediately (2 months ago) but it got gradually worse and recently both Blues were going for the Yellows non-stop and had caused bleeding in both. Interestingly they did not bug the Reds. If the blues went for the Reds, then the Reds (which are bigger) beat the crap out of them for a few seconds, then ignored them. The Yellows almost never fought back and even when they did the Blues just ducked for cover then came straight back.

I tried taking the Blues out during a water change, but the problem started again immediately. I then consigned one blue to the freezer. The second Blue did not modifiy his behaviour, so he too bit the dust. Now all is happy. I'll probably start to introduce some more guppies later. They're much more interesting than Tetras.

So stay away from the blue ones!

just wanna share my experience.

it seems there are some crazy fish out there. last time, i bought about 11 mollies of different colours. On the way back from the shop, I noticed that 1 black molly was aggresive to all the other mollies (while still inside the plastic bag). My instinct told me that it was better to have 10 happy mollies that 11 troubled mollies. So out went the 1 black mollies So far all the 10 mollies are happy. I even have 4 molly babies of different sizes

Update:

I found out what was happening with my aggressive blue guppies (and now I feel bad).

It seems that the yellow guppies may not have been being attacked by the blue guppies. What I saw was not damage caused by biting, it was the dreaded Camallanus worm! It seems my guppies are infected and these nasty little worms look like red filaments that hang from the anus of your fish. I thought it was biting damage. I guess that the blue guppies found the camellanus worms a tasty treat and kept trying to bite them off (they hang out by up to 1cm or more).

It seems that this worm is bad news and most people recommend destroying all the fish infected and hope that it doesn't spread (which it usually doesn't if you only have fish & plants in your tank). However, there is apparantly a treatment that has been newly released as a wormer for reptiles. I'll give it a go on the rest and see what happens.

I lost a few guppies to the viscitudes of the camallanus worm, but have managed to cure the survivor.

Apparantly there are no effective fish targetted treatments for camallanus worm. There are two treatments available for either birds or reptiles (Levamisole HCl or Fenbendazole, usually with Piperazine as a secondary ingredient). Fenbendazole is more difficult to use, there is a danger of overdose.

I tried the easy approach first. I put a diluted solution of Levamisole onto the fish food, let it soak in for 10 minutes then fed the fish (I didn't bother to dry it as some have recommended). I used the dosage recommended on the packet. This had no effect. I then used the solution directly on the food (no dilution). This did work. In three days (three feedings) the worms were gone. By the fourth day the guppy looked completely normal (no swelling, no stretching of the anus).

I have the feeling that my guppies (male) attack the female guppies when they are pregnant. Their whole behavior is more aggressive, also towards the Platies (I have 2 orange ones). I think the male guppies attack those fish, who try to do their "business"
Can somebody explain those above discussed worms more? I wonder if my fish just go to the bathroom, or if they have those worms???


Elli

Hi, I notice that my female guppy is fiercer than my male guppies. It always tries to 'harass' the new born guppy whereas the male guppies do not do that.

Divelli,

I'm new to keeping fish so learned all this from the web and my local aquarist. The worm causes bloat (they look pregnant, since mine were all males I thought that it was constipation). After a few weeks little dark threads appeared around the anus. They were very short to start with and I didn't really notice them. What I did notice is that the other guppies (which came from a different batch) kept 'attacking' the anus of the infected guppies. I later found out that some other fish find the parasites a tasty treat and can try to eat them. After a while the worms became big enough to see that they were red. This worm (camallanus) is apparantly quite rare in tropical tanks as it has a complicated life-cycle. My guppies came with it. Look for the red worm-like threads (some got up to 1cm in length). From what I understand the chances of curing them are ok if you get it early (but the worm uses an agressive hook that can often give rise to secondary infections, even after it's dead). It's not very contagious in tanks due to the complicated life-cycle. If you're sure you've got this worm, then see my posts above for the treatment.

Thank you, Robert That gives me a good Idea what to look for.
I have one female, which is kinda bloated but I do not think I have this worm. I will keep an eye on it. I just bought another female and three days after I bought her, she had 12 babies. So my whole tank is nuts again ... I wrote about it in "Frisky aggressive guppies"...
My fish can not sit still!!!

Elli