Which weldon on to use for acrylic?

[Guerillah]

I notice some people use 4, 16, etc.. which one should I use for my project?

This is what I need to do... This tank had a large 10x10 overflow directly in the middle. I removed it and now I need to cover the sump holes. I plan to use 1/4" thick acrylic (unless someone suggests thicker, the tank is 1") to cover them so there are no longer holes and of course it needs to be water tight. Which kind of acrylic cement should I use for the job and how should I go about doing it? I was going to cut squares out to cover the 4 holes. Here is a picture of what im covering.

Any help is appreciated, thanks

 

[Miles]

I ordered #16 because I heard it had the best bonding properties..


I am not sure about patching that.. I wonder about the proportion of weight displacement.. ?

 

[Guerillah]

Yea, someone told me since the area that im patching is so small (3.5" at the most) that the cell-cast acrylic doesnt have to be that thick... can anyone confirm? The aquarium is 40" tall.