Some very good questions Bill. American Marine has a inexpensive one for about $100 and it comes with a 2 year warrenty, on the down side it does not have a replaceable electrode so that may shorten it's life span in the long run. The American Marine model is easily available from most mail-order pet shops and even some better LFS. If you really want a good quality meter I would get one from a place dealing primarily with meters. E-mail me privatly and I will send you some of these links and telephone numbers or just search the web. To the secound part of your question thats a bit tougher simply because no one value may be acceptable to all species.In this regard we may not generalize. One source is some of the better quality books out there on Dwarf Cichlids that list the Counductivity of the native waters, like the one by Linke & steack. That is our starting point. However tolerances are varied depending on the species we are talking about and whether they are tank raised or wild. One thing you can do is test your source water and then see how it changes over time. The microsiemens go up as the water is polluted with nutrients. For example my source water has a microsiemens of less then 10. In my breeding tanks it stays at about 30-40, for my more demanding species I like to keep it under 50. That means water changes! I am currenty accumalating data in this regard and will be posting it on my web page as a resource for the serious dwarf Cichlid keeper. Check back with my web page for the whole story and continued updates as I can go on and on this subject. e-mail me privatly for any specifics for the species you may be working on and I will be happy to help you out. Good luck. === David Sanchez Casselberry, FL http://www.mindspring.com/~barbax barbax2@yahoo.com _________________________________________________________ Do You Yahoo!? Get your free @yahoo.com address at http://mail.yahoo.com ------------------------------------------------------------------------- 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"!