DIY Carbon / Fluidised Rowaphos Reactor.

If there is one item that is bound to come in useful at some stage or other, and also an item I think every self respecting reefer should keep an eye out for when shopping with the other half, its the ubiquitous Acrylic pasta/spaghetti jar. These really are  wondrous things that don't cost much, but can be made into a multitude of different pieces of kit from Ca reactors, to filters, to Kalkstirrers etc etc. With just a few simple modifications the possible savings that can be gained are fantastic, especially when you consider the cost of some manufactured equipment that are really no more than an acrylic tube as well, with a bit of plumbing attached. So take the chance to go shopping with the good lady for a change (she'll be suspicious but what the hell) and keep a sneaky eye out for them during your travels. You can usually find them in places such as Habitat, Marks and Spencer (home section), occasionally at Asda. Effectively anywhere that sells cheap home/kitchen equipment. There are various types available from clasp top type, to screw top type. The main things to look out for is thickness, height, (volume) and how well they seal. Prices vary from £7.00 to around £15.00 depending on quality.

The  main idea behind this piece of equipment was to design a simple and effective way of filtering the water through two types of media at the same time, specifically Carbon and Rowaphos. One of the big issues with Rowaphos when utilised for phosphate removal is its tendency to compact and bind together when used in the supplied bag, or between layers of filter floss in a power filter. In effect water ends up flowing around rather than through the media, so when it comes time for changing, there is a good chance that a vast majority of what you are throwing away is actually un-used or still active. One way round this is fluidisation. this is where the media is held 'loosely' in a container and water is pumped up through it causing the grains to move around. This inevitably stops the media from compacting or binding and at the same time massively increases its effectiveness. Just like a fluidised sand filter. To a certain degree it will need changing less often as well, due to the fact you are utilising 'all' of the media, rather than just the outer layer.

Combining a lower layer of granulated carbon as well, effectively means he unit can be utilised for either a single media, or combinations. however I would state that at this time I'm still not in favour of fluidising both carbon and Rowaphos at the same time in the same space, due to the fact that in composition, carbon is allot harder than the Rowaphos, and this could quite possibly lead to excessive erosion of the media, and deposition all over your sump or tank over time with Rowaphos powder. Indeed it should be remembered that to fluidise this media, you only need to have it gently bubbling away, not whizzing round as though it were on a spin cycle, or likewise, excessive erosion may occur again. If utilising mixed media it is important to separate them as I have done in this design. Or in the case of very large systems link two together in tandem, and fill each one in turn. Either way, I would always recommend placing the carbon first, and the Rowaphos after as it seems logical that with the small amount of erosion that will inevitably occur, clogging of the carbon would happen, negating its effectiveness very quickly. Likewise its important to feed the unit from a point in the system that is as low in floating particulate matter as possible to prevent premature clogging of the separator sponges or indeed the media. I would recommend either placing a pre-filter on the power head used to feed the unit, or take water from the last chamber in the sump where your return pumps are kept.

The following shots cover various aspects of the building process.

Top Left: This shows an overall view of the reactor with foam separators inserted and a ruler next to the unit for scale. Water enters the unit at the bottom fed via a power head, or Teed off from a return pump. (both methods require a regulator tap to adjust the flow which should be set at about 800-1000lph). After passing through the media, water exits via the top and returns back to a suitable area of the sump. All pipe work, elbows, and bulkhead fittings used are Marley 21.5mm overflow solvent weld, available from your local B&Q warehouse.

Top Right: This shot shows a top view of the reactor with the clasp lid undone. Once fastened, the rubber seal prevents leakages. The top bulkhead fitting for the output runs strait through the lid and is sealed with silicone sealer at both front and back faces.

Left: This is another shot of the unit that shows the output pipe which travels up and over the top lip of the sump and then down, to exit at the water level via an adjustable elbow so that flow can be directed to any area of the sump that requires a little extra turbulence.

Right: This shows the top bulkhead fitting that exits through the lid. Cutting the hole is quite easy. Simply heat a pointed knife over a flame or hob, until red hot. Then simply melt/cut to a pre marked line. Several passes may be required to cut right through the acrylic, but once done, the the flange and seal will cover up any minor indiscretions. It is quite common when cutting acrylic in this fashion, that a small ridge will be present around the edge of the hole. Simply let the acrylic cool, and then just push the bur inwards toward the hole centre. The bur will crack off leaving a neat flush edge.

Left: The bottom bulkhead fitting is done in the same fashion as the lid, however due to the curvature of the container you ill notice a gap around two sides of the joining flange. Prior to fitting you should place a thick bead of silicone round the back face of the outer flange which will seal and fill the gaps when the fastening ring is tightened up from the inside. (this should not be done up too tight or cracking may occur) Simply clean off any surplus silicone from around the outer flange. Once dry and set. the join is very strong and wont leak as the silicone effectively forms a curved sealing ring.

Right: Once the bulkheads are fastened in place the bottom sponge liners can be added. The first is simply a 2" strip of course corrugated pond filter sponge which is pushed down into the bottom of the unit to create a ledge just higher than the top edge of the input nozzle. On top of this, is a course foam circular pad that acts as the support for the first layer of media, (in this case granular carbon) When making the pads it is a good idea to make them slightly larger than the internal diameter of the unit. This ensures a good seal that will stop media from falling down the sides of the foam pads, although not so large that the foam is compressed, reducing its effectiveness at allowing good flow through it.

Left: This is the unit during bench testing for leaks. I did discover at this time that the flow tap 'MUST' be placed prior to the unit and 'NOT' on the output pipe. The sealing ring for the lid 'although effective' will not cope with excessive pressure. By placing the tap 'before' the unit, internal pressure is avoided.

Right: This is the unit running with the carbon at the bottom, a second foam insert to act as a separator and then the Rowaphos bubbling away on top. You will notice a small gap between the outlet nozzle and the top (3rd) sponge insert. This ensures an even distribution of flow through the sponge. If placed too close, granules are forced through the sponge and out the nozzle due to the concentrated area of flow. Some impregnation of the sponge does occur however this is minimal if sufficient clearance is given between the two, and flow through the unit is kept at reasonable levels.

These are close-up pictures showing how the unit was running after two weeks. Some detritus build-up is present although this hasn't impeded flow though the unit at all, and is largely due to me tampering with the tank every other day stirring things up as more work is completed on the system. Effectively the unit will only need re-filling every two months or so once the tank has settled dependant on PO4 levels.

Since installing the unit PO4 levels have been undetectable on a Salifert test kit, despite heavy feeding of the sand beds in the sump and the main tank. It appears that the unit is working extremely well, and the fluidising action of the Rowaphos has maximised its potential for PO4 removal. I will be piggybacking a second unit to this one in the near future, with the intention to run 1 litre of Rowaphos in the second unit whilst retaining the first for Carbon on its own. No increase in pump capacity is required, so it should be a simple case of duplicating the unit and feeding strait from the outlet of the first unit and then down to the second's inlet nozzle.

Notes on filling the unit:

 Only use a large grain Carbon, as this will keep flow though the unit at a maximum, without stagnation or pressure increase (Rowa-carbon is ideal, although any good grade granular/pellet carbon will suffice)

Do not overfill the unit. Po4 removing medias can have a detrimental effect on tank pH levels if over dosed. Always stick to the manufacturers recommended dose/volume ratio....

Prior to putting your Rowaphos in the unit, I would strongly recommend rinsing it through first to remove the tainting that is common, and to remove the fine powder that is present as well. If not done, excessive discoloration of the tank water may result, plus the expulsion of the fine powder all over the inside of your sump/DSB/tank. Although Rowaphos state on the packaging that the compound should not be rinsed, this is not the case when 'fluidising' as it is inevitable that any fine particles will get pushed out of the unit. Start the unit with the flow tap closed and then gradually increase flow though the unit until the Rowaphos just bubbles very gently. Some expulsion is inevitable for the first few hours, although this will subside as the granular/heavier part of the Rowaphos remains inside the reaction chamber. Very little if any of the total volume is lost during this period.

Have fun.

Simon.