How much rockwork do you have? Can we see a pic perhaps? Is it just aggression in general, or are certain fish doing the picking or getting picked on? Sometimes you have to remove extra dem males even with larger numbers.
I'm not sure about the size in gallon. But the dimension of the tank is 48"x20"x20".
Here's the picture of the tank. The tank is exactly 9 months old.
I think it's just aggression in general. It's quite difficult to explain. Please bare with my language... Seems like there're about 4-5 fish that are dominant. About 3-4 fish are definitely at the bottom of the hierarchy which many times can be found hiding head down in the upper corner of the tank or amoung the bubbles. The rest falls somewhere in between. The more dominant fish claim "houses" in the rockwork and stay in front of the houses. The less dominant fish stay "in" the houses and just stick their heads out - watching. When a poor small demasoni swims by, the owner of the house would dash out and chase him to another area, which would be in front of another house and the owner of the another house would dash out and chase him away to another area ... and this keeps going on and on.
The similar story goes for the yellow lab. One dominant yellow lab always stay in the center of the tank. The other 4 always hide.
So, most of the time, the fish refrain from moving about and the atmosphere looks tense all the time. They just don't look happy. (However, there's no problem during feeding.)
- Am I under-stock?
- If I add, say 10 more demasoni, will it help spreading out the aggression?
- Will it be disastrous introducing new fish now?
- Or should I even add more rocks?
There may be one solution which is to add a boss to the tank a fish that will keep all the demasoni in check you could try adding an adult male aurtus it may calm the tank down as he will control the tank and any aggression but it may back fire so be prepeared to remove it if it does not work.
I would not advise the same solution for any other tanks with high aggression but to control 14 demanosi take a tough fish !