TAMING THE TANK BULLY - STUDY ON AGGRESSIVE FISHES

 AQUATIC QUERY

Every aquarist has a story about a fish that turned from a peaceful pet into a fin-nipping tyrant. An aquarist's letter gives us a look at solving this common problem:

I recently bought a beautiful 32×25×3×30 centimeters aquarium. The tank was initially stocked with one red platy, a black molly, and two silver shares. I later purchased a blue gourami. Shortly after introducing the fish into the aquarium, it started pursuing all the other fishes relentlessly. 

One of them (the red platy) got wounded and died two days later. I had to remove the gourami to prevent a further attack of the other occupants. Could it be that all blue gourami are carnivorous? What do I do to this bully?

ADDISSI, O.  Lagos.

Expert Diagnosis 

Your problem has to do with inexperience in knowledge about the type, size, nature, and habits of the new fish you bought. The blue gourami (Tricogaster Tricopterus) is a naturally gentle, adaptable, and well-behaved community fish originally from Malaya and Thailand.

They are not carnivorous since they have a rather small, toothless mouth and live on dried flakes and very small live feeds. Although you did not specify its size, any of the following factors could be responsible for the change in the behavior of your gourami. The four key factors for a peaceful tank are;

* Your tank size, which happens to be too small for an average-sized gourami (10cm). You will need at least a 60x30x30cm (2ft) tank for the fish to swim comfortably without feeling territorial.

* Inconducive environment, like a thinly planted aquarium, should this be the case, I would advise you to buy more natural plants, especially the floating types like the water milfoil (myriophyllum ep), which happens to be the gourami’s favorite.

* Your method of introducing the fish into the tank. How a new fish is added is critical; the correct method involves turning off the aquarium lights to reduce stress and aggression as you introduce the fish.

* The last factor might be the state of the gourami. If the specimen purchased is a male in a mating mood, which is usually identified by a red throat and belly and a pointed dorsal fin, then it will refuse to settle in a new tank unless it is paired with a female counterpart.

Should your specimen be a mature male, you will need to buy a female one.