Switching from internal to external overflows?

TCoach · Oct 30, 2022

So I have a 120 gallon tank with dual internal overflows. I’m wanting to convert the tank to an external overflow peninsula style tank. I’m putting it out in-law suite/office right beside my desk. Since this is a converted garage, there is a ~6” jut out along the bottom of the wall making a good area to have the plumbing out of the way, yet easily accessible.

Looking for some ideas:

1. What is the best way to close up the existing 4 holes in the bottom of the tank?

2. Being 2’ wide, I’m assuming it will be no problem to have 3-4 holes drilled through the glass for the overflow and 2 returns? (Looking to have 3-5x tank turnover max)

3. Would you advise against doing this or for doing this?

Any other words of wisdom?

Thanks,
- TCoach

Quietman · Oct 30, 2022

Those internal overflows can be a real pain to remove. But if you go forward, plenty of options that will work. Cover holes with plate glass 3/8 to 1/2" thick with aquarium safe silicon will work. Think I'd prefer just putting in bulkheads with blanks or short stub tubes. Could use one for a quick drain to help with water changes. Lastly, consider using the existing holes as a closed loop flow system to remove power heads. With the return for the new overflow you could probably skip power heads all together.

You can drill that manyholes in the short side...just follow the general rules on how close to edge and between holes. Check for tempering of course. You could go over the top with returns as well.

Good luck!