What size sump/refugium?

I was surprised I didn't find this on here...maybe I didn't look in the right places.
I figure, though, that many others have wondered this as well.

What size sump should be used for what size tank?
How large should the refugium within it be?
What size return pump should be used?


Any help is appreciated.

Typically with a reef tank an 8-10x turn over in total water volume is recommended.. Be sure that this is 8-10x turn over after head height is taken into consideration
As far as refugiums are concerned, there's a lot of opinions on size and design.. I've found that larger areas with lower water flow but good circulation to alleviate dead areas helps with proper contact with macro algae and encourage growth and nutrient export.. Some guys go with a deep sand bed with macro and live rock rubble and some go with straight with macro algae.. Just keep in mind that macro algae doesnt need fast water flow but steady flow and a good light source for proper photosynthesis and growth.. Without it, algae won't be able to pull as much nutrients out and function as efficiently

I'm sorry. I don't understand 8-10x turn over.
Total sump virgin.

Basically you want the largest sump you can comfortably fit under the main display tank. If you run a 125 gallon tank with a 40 gallon sump, you want a return pump that will pump between 1325 and 1650 gallons per hour. With every pump there is variation as to what they'll pump at different head height. So if your return pump is having to pump water 5 feet high, that is the head height. I usually build my sump to have just enough room for the skimmer in one section and the rest of the room available split in half, one for refugium, and one section for the return pump.

No worries.. Whenever someone talks about water volume turned over, they are referring to the total volume of water in your system being pumped through your return pump, into your main display, back into your sump, and then again being returned to the main display.. This complete cycle is called 1 full turn over of water volume and you're looking for around 8-10 full cycles in one hour.. For example, in a 50 gallon aquarium with a 20 gallon sump the total water volume is 70 gallons.. If you read on the spec of a pump your ideal value would need to be anywhere between 560-700 gallons/ hour at 3-4 feet of head pressure because you loose flow rate the higher your pump must pump your water from the sump to the main display.. And 3-4 feet is pretty standard length in measurement of a sump to return height.. So taking hrs height, total water volume, and flow rate into consideration, you can determine which pump or pumps is best for your system.. Some go with multiple smaller pumps and use individual lines for their returns and some go with a large pump with a single inlet or install PVC splitters to create multiple inlet areas.

I see.
Are there any negatives to running two sumps?

None that I can think of besides more equipment to maintain.. You're adding more water volume that can give more area for modularity depending on what you want to do with it.. If you have the space, go for it

I would suggest the catalina 3000 return pump. I've had great success with them and they don't add much heat to the water because of better efficiency.

A submersible pump is a great and easy way to go but can add a little heat, not much to worry with if you go with a quality one like sparky said.. Dry return pumps are another way to go and the heat added is a fraction of a degree.. Just depends on the size of your tank and the way you want to set up your sump.. As a new guy id stick with a submersible pump for now, it'll get the job done

Thanks, y'all!
I asked about duals because I have two sumps that are probably too small for any of my tanks, but I have a HOB dual overflow...so I thought I might be able to use the two smalls instead of one large one.

I have lots of extra tanks, but 55s are really tall in the stand. Even the 30s are kinda cramped when it comes to height.