how big should the sump be
 

Im planning on upgrading to a fairy large tank 100-300 gallons.

On my 60 i used a canister, never a sump.

I would wana build a sump on my upgrade tank, i heard a sump can realy be any size you want but im a bit confused.

If i have a 300 gallon tank with a lets say a fairly small sump like 10-20 gallons and then theres a power outage wouldn't water drain from the overflow and the pump wouldnt be operating so the water level would quickly raise and flood out of the sump.

So shouldnt you have to have a decent sized sump on a large system?

You definately need to factor in overflow for power failures. That will dictate the minimum size for the empty space in your sump. Then you need to decide on a skimmer and if it's going to be an internal one or external one. If internal, that will give you an idea of how much space you need in the sump for the skimmer. Next you will want to decide if you plan on running filter socks, internal reactors, live rock in the sump, refugium etc.

There is no set rule to sizing a sump that I am aware of. I'm of the belief that bigger is better as it allows for more flexibility. If your sump is going under the tank, my thinking is that you should make it as large as you can fit below while leaving some room for pumps. This assuming you plan on going with external pumps. When I redid my sumps, I had a 4' x 8' space under my tank to work with. I marked my footprint out on the floor with tape and started laying stuff out. That tape on the floor led to my final sump and refugium footprint.

Here is where my design started. I wanted my sump to be as large as possible but because it was replacing a sump on an existing tank that was up and running, I had to factor in the doors below the tank which dictated the maximum width. Given that I wanted it as large as possible I decided to make it 2 pieces. One for the main sump and one refugium. The total maximum volume between the two is 180 gallons.
http://i390.photobucket.com/albums/o...s/DSC00504.jpg

http://i390.photobucket.com/albums/o...s/DSC00474.jpg
Here is a drawing based on my rough layout. I have four 7" filter socks in addition to a pretty large Alpha 300 skimmer.
http://i390.photobucket.com/albums/o...Both-sumps.jpg

Here is the sump and refugium after it was done and ready to be installed.
http://i390.photobucket.com/albums/o...-and-fuge2.jpg

Wow very impressive design. Did you buy it or actually design it.

Why even have a sump if it's only going to be 10-20 gallons? Don't waste your time.

Take your old 60g tank and turn that into your new sump. On a 100-300g system, that's barely big enough to be called serious.

The rule of thumb is, the bigger the better. I have a 180g DT & 70g anemone tank that share a 120g refugium/sump. You need room for a pump (unless you're going external), a skimmer, maybe a reactor or two, you probably should have a refugium and you'll need a fair amount of 'spare' room for power off siphon to the sump. BTW. I did a drain from the top of my sump, thru the wall and out of the house, just in case the sump would ever try to overflow. I'd rather lose everything in the tank than flood my house... again! :thumbsup:

The foot print of my sump/fuge is 60" x 20" x 12" Tall with my tank being 300 gallons. I go 2 to 4 days without adding top off water. I run two external pumps, with only a skimmer and fuge section as constant level sections.

I used a 55 under a 125 and wish I could have gone bigger. You can't have a big enough sump!

I use a 75 on my 90 because I plan to go to a 220 in the near future. Also remember that the ability of a sump to catch the tank overflow in the event of pump failure is also a function of baffle height.

Yes.. It was my own design.

So how should I make my baffles to avoid any flooding?