Brown stuff on the back of the tank

[sniper-sam]

Hi guys
As the title suggests, and it's only appearing on the back of the tank, not the from or the sides.
The tank is a Jewel Vision 450 with Discus, bogwood, giant Vallis and Anubia, substrate is gravel. I also have 2 Eheim 2180 external filters and a UV steriliser operating.
Just before this mornings water change, which is done weekly @ 25% I carried a water test, the results were that the water on Ammonia, Nitrite and Nitrate stayed clear and the PH was around 7.5.
I think I've covered everything so if anybody could help me out with getting rid permanently it would be much appreciated

 

[Cookie*]

I get that stuff on my back wall too, sometimes front, but I usually just scrape it off when I do a water change. I'll scrape it off with a credit card and then start to siphon out water with the filter on too. Once all my water is siphoned, I turn off the filter and clean out the mechanical sponge insert (Aquaclear 110 filter for me) and re-insert. It usually takes about 6 weeks before I even notice it again. It tends to dissolve into the water when I scrape it too, or at least the particles are too small to siphon individually.

 

[BODYDUB]

More than likely it's brown alge, but you could post pics. How many discus do oyu have BTW?????

 

[sniper-sam]

It's not a great pic but you get the idea, roughly 12 discus in the tank, about 2-3" size, one or two are bigger than that though.

 

[ziggy2]

How long are you leaving the lights on? Too much lights can cause that also.

 

[sniper-sam]

Yeah I know too much light can cause algae probs. My lights are on for 7 hours, from 4pm to 11pm and I'm only running the back set at the moment as the front unit had packed in, getting replaced under warranty though.