Discussion in 'Biological/Natural Filtration and Deep Sand Beds' started by Bflynn, 20 Mar 2015.
What would be a good size DSB for a 1800l x 600h x 800w FOWLR setup?
as big as possible, whats the area under the stand?
but something along the lines of 1000x550
space underneath is same size as tank, minus frame work of stand.
1000 X 550 X depth?
well the sand bed should be 12-15cm, plus some water above so 300-400mm high
Minus the frame, your sump could be 700mm wide.
Skimmer compartment, fit your skimmer and see what is the smallest you need for the skimmer. Take into account that you should still be able to take the skimmer out, within the limited head space under the tank. so if you need to twist the skimmer sideways to get it out, your chamber needs to be big enough to be able to do that.
I like the water above the sand to be at least 150mm deep. 200 or 250mm is better. But then again you increase the sump glass height which could limit the removal of the skimmer body. Keep that in mind. Also a lot of today's skimmers have their water outlet at 250mm deep. Meaning they should stand in only 250mm deep water. To be able to have deep water above the DSB, that means you need to put the skimmer on a stand of sorts. high enough as not to flood the skimmer when switched on. plus you still need space to remove the skimmer cup to be able to clean it.
Will you have a ATU chamber? or feed your ATU from somewhere else directly from a drum? If ATU chamber is also under the tank, remember you need to be able to fill it when needed. Plus it will steal space from the DSB area.
Return chamber. Big enough. Water level should be deep enough above the pump, so that the pump do not pull in a vortex or air bubbles from the overflow. Plus a deeper water level will cause less bubbles to be pulled down. Place your pump so that its intake is opposite the divider. Alternative is to put a elbow on the pump intake pointing down so that it sucks in water from as low as possible.
You need to have at least a weekend time span available as a buffer. In case your ATU stops working on the Friday night on a weekend away. So that your return pump do not run dry by the time you get back Sunday night. On average, tanks uses about 10% RO per week. Fans and scrubbers increases the evaporation rate. Your display tank is about 800L. Sump of 1700*700*400 (water level at 400) would easily be another extra 400L. So your buffer needs to be 1200*0.1/7*2 = 34.28, So say at least 40L. So the return chamber needs to hold minimum 40L above the return pump.
If the water level in the return chamber under running conditions are fairly high, you must ensure that your siphon break does work, and you have the minimum volume of water draining to your sump when the power goes out. It does not matter if the water level pushes back and also increase over the DSB at all. Only skimmer in case its sits too deep and floods easily (get a higher stand - if there is space).
Work out those calculations first.
To help you, the return chamber of 700 front to back, and 250mm wide. If the return pump minimum water operating depth is 100mm, that means the minimum volume is 17.5L. Then adding that 40L buffer. That means your return chamber running water depth would increase by another 240mm, actual depth at 340mm That means your last divider must be at minimum 340mm deep. Make it 350mm. That gives you a water depth of 200mm above the sand.
If skimmer chamber is 400mm wide, and return is 250mm. That gives you 1050 by 700 DSB chamber.
That works out to 51% of your display footprint.
If at all you can make the skimmer chamber 350mm, the footprint increases to 53.5%. Not really much.
So, after all this babbling away, have the DSB chamber at 1050 by 750mm. Then you are on about 50%.
If you need to incorporate a ATU chamber. Seeing that you sump is 700 front to back. Your first chamber would be 700 by about 400. That is more than likely enough to get a skimmer fitted. I would use the back part 300mm to make a ATU chamber. That means your skimmer chamber would be 400*400, and next to it RO of 400*300
Say the total sump glass height is 400, that means the RO chamber is capable to hold 45L water. And as calculated before, that's only about 2 days evaporation.
So instead of manually dumping a 20L drum every day into your tank for topup. You will dump 40L water every second day. Woop Woop...
Need to look at an alternative method here.
Thanks at @RiaanP and @dallasg
Would a 1000 x 600 be any good? that would be my size limit on DSB?
The smallest DSB I run in relation to the display was 33%. OK the tank was not overstocked either.
Thanks for all your help!
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