I have used Cole-Parmer pH and TDS meters. A little more expensive than Hanna but I get more consistent readings. I have taken them on collecting trips to the Amazon and Orinoco and they have performed reliably . They also make waterproof meters. Big help. Tom . ------------------------------------------------------------------------- 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"!