I've had a long running discussion going on over this design with several hobbyists since I drew up the plans, as to its effectiveness for feeding the enclosed DSB. The arguments against, are that the DSB should be fed directly from the outflow of the tank and that separating the DSB from the main water flow will reduce its effectiveness or starve it all together.

After looking at various sumps and DSB's I noticed that many DSB's suffer from one or more design flaws that can under certain circumstances negate there effectiveness to just as much 'if not' a higher degree. One concern of mine is the 'what if' syndrome where either the DSB or the tank itself suffers some kind of upset. In this event it would be nice to be able to salvage something of the filtration system or be able to segregate that section off if there was a problem that might affect the livestock. One of my main concerns though, is that we now have a lot higher understanding of the need for strong circulation within many systems (refugium based LPS/Softy set-ups are excepted here obviously due to the need for a more relaxed flow). This need for high turnover puts a large strain on the sump system simply because of the water  velocity involved. Typically a sump will be used as an area where we put all our bolt on goodies such as Skimmer, Kalkstirrer, Ca reactor, etc etc etc that rely on being in areas of high flow in order to disperse their output as evenly as possible. Consequently it is also the area we commonly push water through at an alarmingly quick rate due to the large return pumps we use for system turnover. As such we end up with a slight contradiction in terms. i.e. By definition a DSB needs 'food' to thrive, not just in the form of chemical but solid as well, in order so that it can maintain the high quantities of the worms etc that feed on it. To effectively remove solid waste we have to let the water slow down until the solid stuff falls out of suspension. bit like stirring a cupful of tealeaves. ('As the stirring stops and the waters velocity drops, as does its ability to hold the tealeaves in suspension and they gradually fall to the bottom of the cup.') Its here that the contradiction lies. i.e. 'How can we expect waste/food to fall out of suspension and onto our DSB, when the water in question is whizzing past at some 6000lts per hr plus?. Inevitably only the heaviest particles will settle and the rest is shoved strait back to the return pumps and back up into the tank where we are trying so hard to get rid of it in the first place!. The only way round this apart from having a DSB in the main tank as well, is to separate the DSB from the main sump. As stated before, this also applies if there was problem, and the  sump DSB needed to be separated from the rest of the system for a short while.

We also have a dilemma in that DSB's work much better when they are fed highly oxygenated water for the benefit of all the micro fauna in the surface layers, which is exactly what we have in our high flow areas but as stated before, these areas are effectively out of bounds for the DSB due to solids not being allowed to fall out of suspension. The only other place in the system that we can find highly oxygenated water is the outflow from the Skimmer. This has a big benefit in that the output has a much lower flow rate than the main sump (unless your using a monster of a skimmer), but at the same time its drawback is that it is very low in food for the bed and its life forms. As I said before, separating the DSB and feeding it separately solves the flow rate problem, and adding water from the Skimmer outflow solves the oxygenation problem. My only other problem then was  how to cram all those contradictory requirements into one unit to save space for the rest of the equipment.

This is where the separator design comes in. (See Diagram below).

Key.

 Red (unfiltered mucky water).

Blue. (pre-filtered water).

Green. (food laden, oxygen rich, clean water from DSB)

As you will notice. Untreated water (waste laden) flows down the overflows and drops out into compartment 'A' this is where the bulk of the bubbles are diverted back upwards after hitting the angled baffle. However not all of this water makes it to this section due to the tea-off that steals from the overflows. This 'waste laden' amount is controlled via an adjustable elbow and then drops to the raised DSB compartment 'D', and can be adjusted for flow and food amount. Under normal circumstances the total amount of water being teed off would be 1/6th the total turnover rate of the sump itself. The remaining 5/6ths would be passed under the de-gassing baffle, and into compartment 'B'. It is at this point that water is taken for the skimmer feed via a 1" bulkhead fitting and hard piped to the skimmer, through, and then returned as highly oxygenated water back to the top of the DSB as a compliment to the food/waste feed. The remaining water then flows under the DSB  at high velocity 'C' up, and over the mixer baffle where it is joined by the overflow from the DSB. This outflow is rich in live food for the corals in the show tank and is low in waste due to the settlement and capture of suspended solids and the reduction of Amm,No2, and No3 from the DSB as well. This final mix of skimmed, filtered 'but food laden' water finally flows under the last baffle where a grill 'E' has been placed to prevent anything (stray fish, or macro algae from the DSB) making its way into the final compartment 'F'. Here there are two 1" bulkhead fittings to take water from this section to the return pumps which are housed away from the sump to keep heat build-up to a minimum. It is in this last compartment, that the Kalkstirrer, and Ca reactor are depositing their output into the high flow where dispersion is at its highest and the auto top-up system will be fitted. Any evaporation within the entire system shows up in this area due to the fixed height of the tank overflows and the designing of the sump baffles..

After assembly, it was time to test the theory. So I filled the sump to the normal running height. And connected the two Aquabee 3000's, drawing water from compartment 'F' and returning it to compartment 'A'. All went exceedingly well, including having my suspicions about flow rate confirmed. I feel quite confidant in the fact that it would be quite feasible to increase throughput by over 100% without any problems that's up from 6000lts/hr to 12000lts/hr or 3168 gall/hr. One Test I did, confirmed my suspicions over the settlement and flow rate/velocity issue. I poured some muck from my skimmer into compartment 'A' and timed how long it would take to travel the full length of compartment 'C' and inspected whether any of the solid waste had fallen out of suspension or whether it just got pulled along in the flow. To my astonishment the velocity of water along this stretch of the sump (i.e. the widest section) was in excess of 1ft/sec and only the largest of particles stayed in the bottom without being pulled up and over the mixer baffle before ending up back at the return pumps. Although this might seem alarming it should be remembered that this sump is only 12" wide. If I had been using a 24" wide sump this velocity would be halved although in my case this was not an option due to cabinet space. A worthwhile exercise though, would be to look at your own sump to see how fluid flows through it and to determine exactly how much waste is actually making it right through and back to the tank ?. In action this design is quite simply an effort to control free waste levels within the system as a whole, whilst at the same time ensuring that what waste is present, is either directed to where it can be utilised properly or removed from the system via the skimmer.

The following shots cover various aspects of the design and a section covering the plate sizes is also included should you wish to duplicate this design for yourself.

'Fig 2'                                                                                                  'Fig 3'

'Fig 2 ' Shows the DSB section raised on the four stilts. these were simply made from Air lift tubing silicone'd to the base of the sump and to the DSB base plate. You will notice that the RH end plate for the DSB is higher than all the other baffles including the LH end plate for the DSB. This ensures that water cannot flow back into the skimmer feed compartment where the beneficial food given out by the DSB would be wasted by being skimmed off.

'Fig 3' Shows a top view with a frag tray in place. The four gang valves at the other end, are for the various RO feeds. Water flows direct from the RO/DI unit to the main input and is then split to the Kalkstirrer, Auto top-up float valve which will be plumbed through the back panel at water level in the last compartment and the surplus is then sent to an outside storage container ready for use when doing water changes the fourth valve is a spare.

All the glass used for the internals was 3mm thick apart from the DSB base which was 5mm. and silicone'd in place using pure silicone sealer. It was not necessary to go thicker than this, as there is no pressure internally against the panels except water flow.

The DSB section was then filled with water from my other setup and had a 5" layer of fine Silica sand settling down in it. Over the next few weeks a couple of pieces of uncured LR were added to kick-start the DSB off which was then tended for the next 6 months until the rest of the system was in its new home ready to be fired up. Over this period close attention was paid to feeding regimes and population density/diversity in the bed. I will be adding a section on this process as things progress with photo's and charts comparing the water quality, feeding, and population. One interesting experiment will be the adding of known quantities of old tank water from my old set-up which carries a known amount of NO3 and then observing the reduction rate within the confines of  the stand alone DSB.

UPDATE.......April 2003.

As of April, the sump has been running attached to the main system for three months. in this time the diversity and population of organisms has increased massively. There are a multitude of small snails, tunicates, sponges, worms, pods, shrimps, and sand stars all crawling around looking for any morsels dropped in their way. The macro algae has also taken on a good spurt in growth. All parameters are holding very stable throughout the entire system with a very low NO3 reading of 1ppm and falling.

Flow through the sump has proved very beneficial in the stabilisation of pH, and very effective at controlling waste levels despite very heavy feeding from myself in the interests of increasing diversity within the DSB area. The final baffle has also proved to be of an advantage as a good place for the addition of additives such as Kalkwasser due to the very high flow rate. .

This Photo was taken two months after linking to the main tank. (Feb 03)

This is a Photo of the sump in action after 12 months (Feb 04). Included are the DIY Rowaphos reactor (right) A DIY Calcium reactor ( Left of centre) and the Ratz Kalkwasser stirrer (left hand side)

You can find more detailed info on this and other DSB's, on the following page    DSB's & Live Rock

Have fun.