sumps..did you say sump??
they are not difficult.
bigger is better when considering a sump.
I would go with a 40 to 50 g sump for a 125 but I like bigger.
my 75 has a 20+
my 110 has a 30 g fuge
sumps are pretty simple and you can build one yourself.
what size are the holes drilled?
where are they drilled (bottom is cool as you can set up stand pipe)
basic sump in picture you can change that if you like. you can do DIY sump using a large aquarium and rubbermaid storage containers.