number of discus per gallon?

[angelover]

Can someone tell me the correct number? In my 75 gallon tank I currently have 2 4 in. discus, 1 6 in.angelfish, and a teacup stingray that's about 9 in. from head to tail. Everyone is getting along really well. I would like to add 4 more discus to bring them to a school of 6 like they prefer. Is this overcrowding my tank? Thanks once again to all the posters who have been so helpful.

[White Worm]

6 or 7 would be fine. Make sure you feed well and keep the water clean with at least 50% w/c weekly. More the better for discus. Make sure you QT the newcomers before adding them in with the rest of your fish.

[ShinShin]

The # of discus per gallon will depend on certain enviromental factors. The "standard" rule of thumb is 1 adult per 10 gallons of water. It is a good standard rule if you are maintaining average tank maintainence. If you are slacking off on water changes, wiping down the glass, etc., then 1 to 15 gallons would be better. If you are a waterchange Nazi, you can keep 1 per 7.5 gallons. Wattley reported once in his column that he keeps 10 adults in 75 gallon tanks. Jack's water change routine is 40% daily. I've personally kept 10-12 in 55 gallon tanks, and 24 in 100 gallon tank, but did a minimum of 1 morning water change where I laid the discus on their sides and most days another 40-50% change that evening.

There is one problem with keeping the maximum amount of discus in a closed system like an aquarium and that is the transmission of diseases and other parasites, particularly gill flukes. Gill flukes can reach epidemic proportions in a discus fishroom, while being practicully nonexistant in the wild. The more crowded the tank, the easier it is for the fluke to find it's host, no matter how much water you change in a day.

Mat