Fish attacking each other

Hazarrd

For the most part, this has been happening since I stocked my 29 gallon with 2 Dwarf Gourmis, 16 tetras, 3 Mollies, and 6 coryfish. All of the fish, except the coryfish, have been "attacking" the other fish (I believe fin-nipping is the more appropritate term). What is interesting is that only gourmis will only attack gourmis, mollies only mollies, and tetras only tetras. It's quite consistent. What could be the problem?

Amphitrite

Hazzard, how long has the tank been running, and what are your water parameters?

Also, do you have plants and plenty of hiding places for the fish to feel secure?

Hazarrd

Ammonia - 0, Nitrites - .5, Nitrates - 20, pH 7.2

It has been set up for about 4 weeks.

Thanks.

Lupin

What tetras do you have? Some are quite vicious fin nippers like the Serpae Tetras. Tetras do establish pecking order within their group thus the 'attacking'. Nothing serious unless they just keep shredding each other's fins which will result to fin rot.

What gender are your dwarf gouramis? Two males is a bad idea IMO. Male dwarves tend to become territorial as they stake their territory. Even females will be battered by males.

What are the genders of your mollies? A sex ratio of one male to 2-3 females is fine.

Also try to do a daily water change of 10% to dilute the nitrites.:)

Hazarrd

Blue,

You are the one who suggested I get the 2 Male Dwarf Gourmis.

Lupin

Huh? I don't remember saying two males. I have always recommended a pair(female and male), not 2 or more males in the same tank. Males get very aggressive in a small tank.

Lupin

It was unfortunate I did not see you mentioned both were males.
http://www.fishforum.com/viewtopic.php?p=29330

I did recommend two dwarf gouramis but not two of the same gender.

Hazarrd

So I am going to get rid of one of the gouramis I guess. But I still have 2 Mollys of which I don't know the gender. The place I bought them from said the mollys were too young to be able to tell what their gender was. Is that something I should be concerned about? I think I've picked out the 1 of the 3 mollys that is the one emitting the aggression. I am thinking about just taking that one out. Do I run the risk that circumstances will change when their are only 2?

Thanks.

Lupin

The heck with lfs which does not know anything about fish.

Picture shows a male below. The gonopodium is the fin near the anus that is pointed in shape. The female is the one above.