Hi! Luckily for me, I have never experienced your problem, so I can't be of that much help. My only comments are: (a) Any large rocks or driftwood can displace water, giving you a hard time calculating the exact volume (I would hate to calculate the volume in one of those giant rift lake tanks). (b) If you have an external filter there will be some water in there (probably a negligible amount). (c) Remove any activated carbon before you treat the tank. I hope this helps! William Tracy ________________________________________________________________ GET INTERNET ACCESS FROM JUNO! Juno offers FREE or PREMIUM Internet access for less! Join Juno today! For your FREE software, visit: http://dl.www.juno.com/get/tagj. ------------------------------------------------------------------------- This is the apistogramma mailing list, apisto@listbox.com. For instructions on how to subscribe or unsubscribe or get help, email apisto-request@listbox.com. Search http://altavista.digital.com for "Apistogramma Mailing List Archives"!