How often should I remove water with my syphon and add new water? I was doing this once a week but had a very high mortality rate. The receptionist at my doctors office said to stop removing water, and only add treated water when the water levels get low. Wouldn't this cause a lot of ammonia from the waste?

It's a 21 gallon tank and all I have left are platy's. Have lost about $100-$150 worth of fish this past year :(

We used to do our discus tank about 10% a week or if we got lazy just 20% every 2 weeks. They were breeding like crazy and they are supposedly hard fish to get to lay eggs let alone hatch them.

My guppy tank I have here gets syphoned about once a month and I just top it up when it gets low in the mean time, but I have neutralizing blocks in the water that automatically release when the ph changes.

Thanks Shaz, I'll take a look for the neutralizing blocks.

They just look like those long term feeding blocks, white kind of chalky looking but as soon as the ph changes even slightly they start to break down and automatically fix it. It doesn't solve the ammonia problem but it keeps the water at a nice even ph all the time.

I think I know wxactly what you are talking about, do they come in 'fun' shapes? Like a turtle and shells?

I have shell shapes in mine :D
They put oxygen in the water too if you don't have an air stone.

http://www.getprice.com.au/images/uploadimg/191/120_9619.jpg
http://www.getprice.com.au/Aqua-One-Aquarium-Oxy-Block-Gpnc_363--54282089.htm