My fish tank was dirty so I cleaned it the same as I always do.Since then everything in the tank is turning brown.I cleaned it again and the brown is back.It is getting darker and darker .What is my problem and what is the difference between brown and green slime in the tank.Will my goldfish be ok.

You may have brown algae growing which is actually diatoms. If that's what's growing, it should come off easily with an algae pad or even just a finger rubbbing. Diatoms like silica and low light levels. Brown algae/diatoms are not harmful to your fish. Another possibility is that if you stirred up a lot of debris, it could simply be settling on the ornaments and things.

My tank algae page - http://www.fishpondinfo.com/algae.htm

Thanks Robyn for the info.I wasn't very happy with the tank and how the fish were doing.I went out and bought a new tank and everything I needed to get started again. I also bought a pleco. I moved the goldfish over to the new tank and they are doing so much better. They are more lively than I have ever seen them before. I left the pleco in the old tank so it would have some food because the new one is to clean for it (I think).The next morning the pleco was dead.Do you think I should wait awhile to get a new one and also a bigger one?The pleco I bought was very small.
The new tank has a light on it.Do I keep the light on all the time or just at night. The tank is in the corner of a room beside a window.

Since you just got that pleco, it's hard to say if it died from a pre-existing condition, shock from the move, or from the water quality in your tank. You said the tank wasn't very clean so maybe the water quality was enough to finish off the pleco. I would wait a few months for your new tank to get established and then maybe try a pleco again. The size shouldn't matter as far as whether or not it will survive. It's strange in that I've found plecos to be extremely hardy but yourself and many others who have posted in this forum have trouble keeping them alive, or at least newly-purchased ones. I wonder if there is a specific reason.

I run the lights on my aquariums from 7 am to 6 pm. The lights should be off at night so that the fish can sleep.