I test 4 times a day with an iV on my 75 gallon as well as 4 times a day with a Carer on my 35 gallon. Both get dumped back into the tank. I’m a huge Hydros fan, but I like the Carer better for testing. Easier and more consistent results, IME/IMO.I dump the waste back into the sump on my iV and it is a 4 to 1mix. I was running the KH Carer and the iV for several months and dumped the waste from both back into the tank. I was testing 4 times a day. I had no issue.