Hello! i work in a petstore and we need help! we have a fish tank system with sump tank and all! it's about 150 gallons all cycling together. we have had our fish in there with no problem for a year and a half. a few months ago we got in a. shipment of fish and after putting the fish in we experienced a huge loss. almost every fish we had died within the next 2 days. We have been working on this for months. automatic purges, manual water changes, adding prime, adding API water conditioner, adding bacteria PUR balls , and testing our water and everything. our fish tanks got a very bad sewage like smell which went over a couple days. the PH has been high so we added PH down and we've added so many different things. we had a CASCO tech come, a plumber, an electrician, and everyone in corporate. we can't fix our ammonia levels. using the API test kit the ammonia level is as dark as the chart will show and everything else is fine. does any one have any ideas at all??? we are stumped and miss our fish.