Very interesting Doug. Also things going anaerobic will probably crash the pH as well. Some other parameters for the discussion: One thing that I don't think anyone has mentioned so far in this discussion (forgive me if I'm wrong) is that Cardinals tend to love the pH being on the low side, and require this from birth to reproduce....., and I know they can handle pH crashes well. Harlequins too (if good stock) can handle pH crashes but not to the Cardinals level. The catfish (if air breathing enabled - Corys etc) and labyrinth fish you would expect to survive better if the general oxygen levels dropped, and both can moderately handle pH crashes. But in the honey dwarf gouramis quality of stock is also a parameter. Scot Gillespie ________________________________________________________________________________ This message has been checked for all known viruses by the Star Screening System http: //academy.star.co.uk/public/virustats.htm ------------------------------------------------------------------------- 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"!