Brown layer in reservoir

[oerekum]

I'll have to state the obvious. 1.5 years with the same liquid? Not even a drain/refill? Be glad it's just brown...........

But folks have posted good remedies, I hope they work, it should..

Haha suppose you're right. It's only a residue though, the water itself was quite clear. It just left a brown trail in the res, and inside the tubing. It's weird it looks like sand inside the tubing.