Sump/Refugium

Question
Hi,
I have a 70 gallon tank. I plan on setting up a sump/refugium. I was wondering what size tank I would need for an appropriate sump. I would also need to know what size overflow box/pump I should get.

I know that sumps/refugiums should have 3 separate chambers. I was planning on putting bioballs/a filter in the first chamber, macro algae/java moss/heater in the second chamber, then a protein skimmer in the last chamber. I was wondering what your thoughts were on that setup. I will take any and all suggestions.

Current tank specs:
70 gallon tank (approximately a year old)
2 white lights
1 blue light
1 Fluval 205 filter
1 Trio 3000 filter
1 30g power head
1 heater (heated to about 78 degrees)
1 bubbler
I replace 5g of water every month using RO water
Salinity 1.023

Currently in the tank:
1 blue damsel
1 cleaner shrimp
1 pepper shrimp
1 hermit crab
2 snails
3 Fiji rocks
4 bass rock
1 orange tree gorgonian
Crushed coral and sand as the bottom

Future goals:
I plan on putting as many different type of marine plants (different gorgonians, anemones, sponges, etc...), different type of hard to care for tropical fish (angel fish, different kinds of tangs, sturgeons, dolphin fish, clowns, etc...), as well as live rock.

Thanks!!

Answer
"I have a 70 gallon tank. I plan on setting up a sump/refugium. I was wondering what size tank I would need for an appropriate sump. I would also need to know what size overflow box/pump I should get."

I would use at least a 20 gallon long for your sump, though it can be hard to fit all of your filtration in one, so either a 30 or 40 gallon would probably work better.

"I know that sumps/refugiums should have 3 separate chambers. I was planning on putting bioballs/a filter in the first chamber, macro algae/java moss/heater in the second chamber, then a protein skimmer in the last chamber. I was wondering what your thoughts were on that setup. I will take any and all suggestions."

Your plan sounds like it should work pretty well, however, I would suggest one change. Protein skimmers need a stable water height to run consistently, and the level in the final chamber of the sump will most likely change due to evaporation. I would move your protein skimmer into the first chamber and incorporate your mechanical filtration into that area as well in the form of sponges or filter socks.

You should also avoid bio-balls or other forms of bacterial colonies in your sump. If your display is properly stocked with live rock, than bacteria should have plenty of space to colonize there. The advantage to this is that rock in the display can be kept clean by stronger current as well as scavenger animals.