Hello, thank you so much for your reply. It is silvery and it wasn’t there yesterday or atkeast this big. And yes the sump was low last night, I could hear the pump and I thought I filled it with RODI pretty quickly. Can that cause this? Do I need to quarantine it or should I wait?
If it is supersaturation, it can't be treated and isn't contagious in the usual sense.
Here is a section from my fish disease book on the topic:
Acute supersaturation
This is known as the “gas bubble disease.” An aquarium that has a water pump malfunction of some sort may develop a dissolved gas saturation level of greater than 120%. The onset is sudden and the results devastating. Fish will develop severe bilateral exophthalmia (pop-eye involving both eyes), and their gills will show massive trauma with gas bubble aneurysms. In the worst cases, air bubbles will be present in the soft fin rays and in the gills. Death is rapid, and even if the still-living fish are moved to a new aquarium, they will usually not recover
Two common causes of acute supersaturation are a sump that is allowed to run dry, allowing the pump to suck in air, or a loose fitting that allows for a continuous air leak at the suction side of a pump. Despite best intentions, equipment sometimes does fail, allowing supersaturation to occur.
In these cases, the problem can be lessened by always having the return line from any aquarium pump return water to the aquarium above the water line. The agitation of the pumped water hitting the aquarium surface is akin to shaking up a can of soda pop and driving off the “fizz.”
Not every case of gas buildup in animal tissue is caused by supersaturation. Some bacteria produce gasses as they grow and multiply. A fish with a serious bacterial infection may develop gas pockets in the intestines, behind the eyes, in the air bladder, or even under the skin.
Jay
