OTS, is a condition where over time, the aquarium begins to poison itself. Most are blaming it on toxic metal build up from frequent water changes, but some have postulated that the DSB
is a time bomb waiting to go off. Some have theorized that the byproduct of the facultive bacteria that convert nitrate to nitrogen gas (in the absence of oxygen) is hydrogen sulphide and methane and nitrogen. They go on to say that the build up of hydrogen sulfide in the lower layers of the DSB
begins to kill the layers from the bottom to the top slowly. They say the process takes about 4-6 years. This time frame also coincides with DR Ron's toxicity time frame.