internal overflow

Good day everyone. I just got myself a 125 gallon aquarium and I am trying to absorb all the information I can about running a set up this large. I have decided I would like to run a sump with an internal box/tower. My question is, instead of having the water overflow the top of the box could...

So, my tank is already drilled with overflow boxes. I have 2 internal O/F boxes with 2 holes in each. Now, my question is, can I run Bean Animal like it is, and if so, how? Or should I try to replace my existing boxes with the internal/external boxes that have the 3 holes drilled in the bottom...

So, I purchased a tank recently with a internal overflow. I have a Synergy overflow on my other reef I plan to install on the new reef. As I was contemplating how to plug up the holes in the bottom after removing the internal overflow, an idea came to me. Why not turn the existing holes into...