Clogged internal overflow?

[catdoc]

Does anyone have to clean their internal overflow? My overflows seem to be running slowly and I'm wondering if there is something (algae or other muck) blocking the flow of water from the tank into the overflow. The water level in the tank has jumped about a half inch, to where now there is barely any "overflow" effect at all. If I hold the siphon hole on the durso closed, the siphon will clear the water in the overflow chamber in a second or two, so I don't think there's anything obstructing the plumbing outside of the tank. I tried decreasing the flow from the return pump (although I hadn't had to do that for 2 years, why now?) but that didn't help. I'm worried that I'm on the verge of a tank flood if I don't fix this!

The tank in question is my 125 and it has dual overflows. I have a dsb, so the bottom grate on the overflow is pretty well occluded with sand (always has been though). I'm having some algae issues (bubble and hair) in the overflow chamber itself, not as bad in the tank b/c the clean-up crew manages it pretty well. I just don't know how to get in between the two layers that make up the wall of the overflow chamber to clean it out. Or is it another problem altogether?

 

[Toddrtrex]

Are all the teeth of the overflow clean? I know that mine will get blocked up and I will have to take a pipe cleaner brush to them.

 

[maroun.c]

could be some alga that has been sucked or some sand that has accumulated in the tubing...
I sould try to drain the overflow as you state that now there is no overflow efect so there might eb arisk of floding if your tank doesn't take the excess water when you turn the pump off.
Then the first thing I would try would be pumping water in the opposite direction with a strong pump to see if it manages to push something out. then if this does not work I would buy one of those small brushes that come with very small and flexible tubing that you can insert in the tubing and push forward till the end and then backwards a few times to clean the tubes from the inside.

 

[catdoc]

The teeth are clean, tried that but it didn't help.