What is the GH
(general hardness), KH
(carbonate hardness) and pH of your water supply?
This information can usually be obtained from your water supply company's website or by telephoning them. If they can't help you, take a glass full of tap water to the local pet shop and get them to test it for you. Write the results down (in numbers) when they do the tests. And ask them what the results are in (eg: ppm
, dGH, or something else).
Depending on what the GH
of your water is, will determine what fish you should keep.
Angelfish, discus, most tetras, most barbs, Bettas, gouramis, rasbora, Corydoras and small species of suckermouth catfish all occur in soft water (GH
below 150ppm) and a pH below 7.0.
Livebearers (guppies, platies, swordtails, mollies), rainbowfish and goldfish occur in medium hard water with a GH
around 200-250ppm and a pH above 7.0.
If you have very hard water (GH
above 300ppm) then look at African Rift Lake cichlids, or use distilled or reverse osmosis water to reduce the GH
and keep fishes from softer water.
I wouldn't add anymore fish for the reason Aiken Drum mentioned above, basically lots of big fish in a small tank. An Oscar would kill most of the smaller fish in the tank. A blue Acara might work with what you have but not in that tank. You need a bigger tank or get rid of the big fish and get smaller ones.
If you post a picture of the pleco, we might be able to identify it for you?