Why and what is this brown fluff?

I have a 650 litre fresh water community tank and have never had this problem in the 13 years I've had the tank.
Suddenly there is a layer of brown fluff like substance building up in the rock crevices and on the gravel
and the water has a strange smell.
I regularly vacuum this stuff to waste but after a few days its back.
The PH and ammonia levels are fine although the nitrate level is high.
Is this stuff a type of algae and short of plenty of water changes, is there a simple solution to this problem?

 

Do u have a pic of what u are talking about ?

 

NO. I need to take a pic of before and after. Will do.

 

Ok then. Maybe we can find out. What it is

 

Diatoms?

 

How long are your lights on for? If your nitrate levels are high then that could be the cause, try get some filter media that removes nitrates. As far as I know diatoms only appear in newly setup tanks. Try reduce your light hours, feeding less and get some filter media that reduces nitrates.

 

My lights are on for 6 hour a day. Waiting for this fluff to build up again then I will take a pic.

 

Sounds like BGA (blue green algae / cyanobacteria). Usually grows on ornaments, glass, substrate. Its caused by high phosphate and low nitrate levels.
Will have to check the pics to confirm but in the meantime google it and check for yourself.

If it is in fact BGA, DO NOT REDUCE NITRATES. This will cause it to spread quicker because this bacteria hates nitrate and will therefore thrive.

 

I googled it. Could be except it is brown. The white gravel will be covered with a brown "blanket" and when vacuuming it
moves up the vacuum tube like bits of cotton wool???? (hard to describe)

 

Yep sounds like BGA. Although named "Blue Green Algae" it can present itself in many different colours.

Read this article. It is very informative.

Freshwater Saltwater Aquarium Fish Tank Forum

 

Sorry for the delay. Had camera problems. Here is a pic taken before then after vacuuming to waste. I tried to get the colors as close to reality as possible.

 

Looks like detritus, which is biological waste from fish, food and plants that accumulate in corners not reached by filtration. Check your filtration, add a powerhead to stir it up to get it into your filter. Vacuum the gravel every time you do a water change.

 

Is it normally so brown?

 

The pic using flash with the tank lights on resulted in a slightly blue tinge.
Using photo shop I corrected it to basically look as it did. Answer is YES maybe slightly lighter.

 

I do vacuum when I do a water change. I have a weir filter system. Possibly the flow is not strong enough.
When this first started it appeared within days of vacuuming. This time it has taken much longer.
I have no plants in the tank.

 

It has to be algea then

 

It will appear within days as the suspended particles settle on the ground and accumulate in areas with little flow, try to add a small wave maker or powerhead to keep things suspended and get it through you filter. What is the flow rate of your filter?

 

All I can say is that it's a slow trickle over the weir. I will remove the pump. Maybe it just needs cleaning after all these years.

 

Is it loose or stuck on the substrate

 

Like fluff, very light. Easily lifts up when vacuumed.