[JOEYRM7]

I followed what I thought were the normal procedures for doing a FW dip on a yellow tang with black Ich. I had prepared RO/DI water, temperature adjusted, and slightly higher in PH (my tank is at 8.2 and the dip at 8.3-8.4. (I assume that I don't have to chemically dechlorinate the RO water) The water was prepared about a week ago if that makes any difference. I dipped him for about 7 minutes and 3 minutes after putting him back into salt he was dead.
Where did I go wrong? I need to dip another fish but am afraid to until I get some feedback. Thanks

[the_blue_tuna]

First off welcome to Reefland and secondly sorry about your fish. My guess would be that the fish was dipped for a little too long . Here is some material on freshwater dipping ......

http://www.wetwebmedia.com/dipsfaq2.htm

Hope this will help out.

[JOEYRM7]

Thanks for the response. If the problem is time related that's fine and easily correctable.

[Bughead]

I'm so very sorry about your tang. You did everything right as far as procedure. Even length of time was OK. I've FW dipped for as long as 30 minutes. The thing is, FW dipping is a last resort, and your fish was probably already too ill to recover. I've had this happen too. I once lost a yellow tang immediately after a prophylactic dip of about 3-4 minutes. He had been a healthy fish at the lfs. If you ever have to do a FW dip again (remember, LAST RESORT ), adjust the salinity to 1.009 as well as the pH to match the tank. The addition of methylene blue adds available oxygen which also helps with the stress.
Again, I'm so sorry.

[Penguin]

Bughead has given you good advice. I'm not a big fan of freshwater dips as IME they can sometimes cause more harm than good. But it's better than nothing if you don't have a quarantine tank for new fish. I've dipped for 3-5 minutes in the past, but I think a reasonably healthy fish should be able to handle 7. Individual fish might react differently so it's hard to predict what will happen.