unhappy discus

Question
Hi, I have a 150 gallon tank, It has One dragon discus who is not eating and has had a dramatic change in behaviour in the last week with hiding etc. The other occupants are 2 golden algae eaters and one green barb.
I recently purchased this tank and spent some time learning how to cycle the tank and the importance of it.  In the process I lost 5 out of 6 barbs.  I regularly tested the water and visited my fish shop and they assured me I was ready to purchase some serious fish. I got a bit carried away and purchased two dragon discus, the chap in the shop thought they were a pair and on this basis I purchased both of them but unfortunately one bullied the other especially with feeding and despite trying to feed them at opposite ends of the tank one died about a week after I purchased it.  The barb who i thought might become a pest went into hiding and didnt seem to concern the discus at all - the deal with the shop was I could take it to them if it became a problem.  I  put the death down to stress as the other discus seemed fine.  It did die about 3 days after I took 10% of the water out and replaced it with our soft rain water that we have here.  I wondered if the temporary temperature drop bothered it.  All went well for another couple of weeks but again, about 3 days after taking off some water and replacing it, the second discus is behaving the same, it is much shyer and not eating.  It is really only a matter of time I feel before it dies.  Any advice would be greatly appreciated.  The two algae eaters are as happy as pie and the barb is just the same  (It hides most of the day while the lights are on - there are quite a few plants and a piece of drift wood in the tank, and is quite active in the morning and evening.  Many Thanks Karen.

Answer
Hi Karen

Discus are one of the most difficult fish to keep. Their water quality must be superb. They are not for a partially cycled tank. You must do 30% water changes every week. Replacing the tank water with rain water is not a good idea as the chemistry is different from your tap water. You must use water from the same source with each water change to keep the water stable with no fluctuation in pH. Discus need a pH of 6-7 and a temp of 82-86 degrees. When you do your water changes, the replacement water needs to be close to the same temp as the aquarium water. You'll also need to treat the replacement water with a quality water conditioner such as Aquasafe or Stresscoat.

I would try doing a 50% water change using the same water you filled the tank with originally. Keep the temp stable and see how your Discus does.

Hope this helps you, good luck!

Richard