Black Fur in my Tank

Hi

I have an aquarium tank and have lost 5 fish in a week - I have noticed a black fur like something growing on my rock, (looks like fluff)and shells and basically everything in the tank!

Tank was cleaned and water tested 2/3 weeks ago. No new fish or anything

Anyone got any ideas

Found you a good advice for such situation as I searched the subject http://www.aquariacentral.com/forums/archive/index.php/ t-77701.html

The true siamese algae eater eats probably the widest range of algae, including red algae and sometimes beard algae. However, the true SAE can be hard to find at times and similar fish are often sold as SAE's that are not as versatile in eating algae.

They also get quite large, though they don't tend as much towards the type of agression that chinese algae eaters can develop, so you'll want to do a little research first to see if they'll fit in with your current inhabitants and if you have the room for them. Most folks I know who keep them for algae control keep a rough ration of 1:20 gallons.

As for your hardscape pieces, a 4-5 minute soak in the diluted bleach solution followed by a good srubbing with a new toothbrush, then rinsed well with a dechlorinator should get them clean. Thick leaved plants can be dipped in a diluted bleach solution at 1:19 ratio for 2-3 minutes, leaving the roots or rhizome out of the solution. Rinse as above. You'll see some leaf wilt and discoloration and some plants may not recover, but it will kill the algae. Small leafed and more fragile plants are as like to die as recover
from a bleach bath, but you can try a 1-2 minute dip. A complete blackout of the tank for 3-4 days will usually also kill all the algae, but be ready for the fallout of that much material dying all at once.

Please inform me if the problem is solved.

Thank you for your help.
Will let you know how it goes!!