Drilling the Marineland 300DD

I wanted to setup a BeanAnimal Silent and Fail-Safe overflow. From all the overflow systems that I have seen, it makes the most sense and appears to have a good success rate. I tried to get a custom Marineland Deep Dimension tank, but after months of waiting for a quote, bought a stock 300 DD and going to make it myself. That way I get exactly what I want and I save serious $$$ over a custom tank.

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.