What do you guys know about chloramine? Many know, that it gets used from municipalities to treat tap water. It is much more stable than chlorine. So when it comes to supply tap water on long distances, chloramine is what gets used. Chloramine doesn't really smell like chlorine. So using your nose to detect chloramine in the water won't work. Many know, that chloramine is basically chlorine and ammonia. Many know, it is written on bottles from water treatment agents, like Prime from Seachem. A few of you, might know how to remove it. A few might know, that you can not remove it via reverse osmosis. If you run a new RO unit with carbon filter, most of the chloramine gets taken out of the water. And if you run a carbon filter on your tank, you will probably not even know, that you added some chloramine with the RO water into your system. Removal of Chloramine Chloramine can get taken completely out of the water with carbon. The amount of carbon needed, is roughly 3-6 times more than the carbon filter from the RO unit contains. And carbon filters have to be replaced on the recommended schedule, even though your TDS reading is still fine. Simply is the use of products, like Prime from Seachem. There are test kits available for the detection of chloramine, but I doubt that somebody stocks it. Chlorine test kits might not work as there are different kinds of chloramine. Prime from Seachem (250ml) treats 10.000 litre RO water, for the price of R125. What happens when chloramine is added to your system? Depending on the concentration of chloramine in the top up water and also depending if you have an auto top up system running, you will add constantly a bit or once per day/every second day, a couple of litres RO water to your system. The "constantly a bit" is the less harmful variant. In sea water, chloramine breaks down over a few hours, into chlorine and ammonia. Chlorine disappears via surface or skimming. Ammonia gets neutralised, if your filtration can handle the extra load! The most dangerous part about chloramine in a marine fish tank! Chloramine passes through the gills of fish and enters the blood stream. There, it reacts with hemoglobin, forming methemoglobin. In fathead minnows (Pimephales primelas) exposed to 1 ppm-Cl of monochloramine, for example, about 30% of the hemoglobin is converted into methemoglobin. The fish then suffer from anoxia (low oxygen in their tissues) because they have lost some of their hemoglobin, which is responsible for carrying oxygen in the blood. Source and full article: Chloramine and the Reef Aquarium by Randy Holmes-Farley - Reefkeeping.com It results in fish swimming not much anymore, fish turns blind, fish is breathing heavily, etc. Guys who have issues with ammonia and can not figure out why their bloody filtration isn't coping. This might be your answer: Chloramine I did water changes, checked for a high iron content in the water, treated fish with medicine in the feed, put fish into quarantine onto Myxazin. Nothing helped. Of course not, I was adding RO-water with chloramine. Last thought was to polish up the water with something and I came across a bottle of Prime from Seachem. The word chloramine jumped into my eye. I've never heard about it. After some research I was sure, that is the problem. Chloramine in the tap water, which passes the RO-unit. In the meanwhile, the remaining fish are doing fine and recovered. I lost almost all my livestock, just because I could not figure out, what makes a fish blind, why are they breathing so heavy, where other fish in the same system were doing fine and laying eggs. Diseases and parasites, that what I was looking for. The simple answer to the problem, the RO water could be the cause, didn't cross my mind as the TDS reading was okay. Low nitrates and a huge load of old filter media, didn't make me think of that there might be ammonia in the water. The good new is, I know now what went wrong. I know how to prevent such problem in the future. I highly recommend the treatment of RO water used in your system to prevent what I have been through!