Tank Issue

[Nanie]

Hello! I had a question, and I am not sure that the Copy and Paste questionnare applies here, becaues the fish are not sick, that I am aware of. I also do not know a lot of answer to the questions, like PH and that.

We have a 30 gallon tank, with a few fish in it. We bought the tank from an elderly couple. When we bought it, it had some black "stuff" in it. I brought it home, cleaned it out, and we refilled it, adding the tank salt. Well, a few weeks later, the black "stuff" was back. It quickly overtook the tank. I took my fish out (shark, algae eater, some other tropical fish).

When I emptied the tank, I began to really look at what this stuff was. It was all over the rocks, the log, the walls. It is black, it loks fuzzy. It looks hairy in the water, but when you dump it out, it just looks like a black mass. I could NOT get it off of stuff. I had to throw out the rocks, the log, everything. I also scrubbed the tank. It was almost impossible to get that stuff off. I finally took a razor and a magic eraser to it, and got it out. It took a couple of hours.

Well, it's been gone about two months. Nothing has changed, we have just been using tropical fish flakes, and some treats like dried shrimp. Now, within the last few days, it's coming back strong, in the front of the tank.

Can someone tell me what it is? And how to get rid of it?

 

[Ludwig Venter]

Soooooo many questions comes up before either diagnosing or suggesting anything in this case, cause it could be anything.

How often do you change water and how much?
Where do you live
What type of lighting do you have in there and do you switch it off
Is the tank exposed to direct sunlight and for how long
What type of gravel do you use and how old is this gravel
What filtration do you use and how often is it cleaned
How often and how much do you feed
Is it a slimy black substance and is it reddish black (when dry) greenish black or greyish black
What type of algea eater do you have in there