... glue an overflow comb to corner overflow.

I have used silicone before and the comb fell off. and I sanded the comb to give a rough edge to stick to as well.

The overflow is the plastic ones from HFF and the corner overflow is glass. The silicone stuck to the glass but the comb came off clean.

Do people use normal silicone?

What should I use?

Hi. I'm not familiar with the apparatus that you're dealing with but I'm wondering if it's possible to drill small holes in the plastic so the silicone goes through it and can be smeared over to sandwich the comb in place :dunno:

I have found that hot glue guns will work on some plastics where silicone will not.

Drilling holes could be a good idea.

Hot glue wouldn't stick to glass though would it. And being submerged in water...?

The hot glue will be fine in the water, well most of them are from experience but I guess it would pay to check the stick before using it. And it doesn't have to stick to the glass, it will stick to silicone.

the drilling a few small holes idea will work and will be easy to get off later on otherwise use super glue gel ( which will be safe to use with water in the tank)