So I first have to drill out the holes for the overflow pipes. According to BeanAnimal, you need 3 holes. I like to over-engineer things so I’m drilling 4 holes. I am setting it up as a peninsula tank, so the holes need to be on the end of the tank. The tank is too heavy to lift on its end, so I have to drill it horizontally instead of the usually vertically where you can make a putty ring holding water.

Of course, you will void your warranty (I assume). Also, I’m not responsible if you crack your tank doing this. It was my experience that it worked without a problem, but your mileage may vary. You’ve been warned.

I made a quick template out of plywood. I put plumber’s putty around the hole. The putty will make a seal on the glass and help keep water on the hole as it is being drilled.

Here is the template clamped to the side of the tank. You can see the putty makes a nice seal.

I drilled with one hand, spraying water out of a squirt bottle with the other. The plastic box catches the water and glass dust. I drilled relatively slowly, but not that slow. I used bits from glass-holes.com.

In the below photo you can see that the hole is partially drilled. The bit stayed very cool, not even warm.

On the first hole, I had a bit of blowout which caused some splintering around the hole. For all subsequent holes, I clamped some scrap MDF on the inside. This gives the hole some pressure around the edges so that last bit of glass won’t splinter. The remainder of the holes drilled much cleaner.

Nice and smooth.

All 4 holes drilled.

When you are done, you should have some new coasters.

I wanted to do a custom tank but the cost and delay (7 months and no accurate quote!) was too much. I decided to get a stock tank and make my own mods. More fun and way cheaper.

So the first thing is to ditch the overflows. They are siliconed in, but it appears they are added after the tank is put together. I’ve included some photos of when I did it. Of course, this probably voids your warranty — you have been warned. Also, if your tank leaks or blows up afterwards, don’t blame me.

I carefully slipped a razor blade behind the overflow and drew it down, but not all the way. Stop just above the base silicone that holds the bottom and side together. After freeing both sides you can push the overflow out.

Here is the left over silicone at the base. You can see that the bead was added after the main glass pieces were assembled.

Then just clean up the rest of the silicone from the glass.

I didn’t bother trying to get the little bit that overlaps off. It isn’t noticeable especially once sand is in the tank. No point making a weak point in the silicone.

A nice clean tank without overflows. I am still debating what to do about the holes in the bottom. I could put in the bulkheads that came with the tank and cap them. I’m never going to use them, so I may just silicone a largish piece of 3/4″ plate glass over that whole area.