Having already looked at a couple of cone skimmers in our recent reviews, we thought it would be interesting try something a little different and to investigate some alternative designs. Specifically, we were keen to test out a recirculating skimmer design in our system amid rumours of enhanced performance.
Before we look at the skimmer in question, if you aren’t really sure what the difference in these designs is, let’s start with a brief explanation. While the cone skimmers we’ve previously looked at basically just use their pump (or pumps) to both supply water into the skimmer body, and to introduce air via a venturi fitting, a recirculating design uses a dedicated pump (or multiple pumps) to circulate and aerate water in the skimmer body, but a separate feed pump actually moves water through the unit. This gives rather more control over the ‘dwell time’ of water in the skimmer body. Such a skimmer can also be run externally of course being essentially a sealed unit with just the feed pump sitting inside the sump or aquarium. As well as these advantages though, take note that this design is likely to use more electricity and sockets with the additional feed pump running. Also, although theoretically feasible, it is extremely difficult to prove that the technique does actually improve skimmer efficiency.
Anyway, for our test we chose a Hydor Performer Hi-Tech Skimmer 800 Series 2. As with previous Hydor equipment we’ve used, this unit is really easy to assemble consisting of precision parts. It also generally ‘feels’ good quality and benefits from numerous thoughtful design features. Firstly, the unit has a skimmer cup that fits securely to the body with both a rubber O ring and a locking collar to hold it securely in place (although note that smaller versions of the skimmer feature only the “O” ring seal). The cup also features a nice wide drain so it can be connected up to a larger skimmate reservoir if needed. Finely tuning the water level in the unit is really easy using the large, knurled dial. Size-wise, this unit is also very compact with a footprint of just 8.1 x 12.6 inches and a height of 22.4 inches (take note though that the outlet pipe must be positioned above the water surface). On paper, the power consumption of the Seltz L45 SK which does the mixing is listed as 25 watts ‘real consumption’ and we’ve also seen a figure of up to 50 watts. The actual figure is therefore likely to lie within this range and makes it good to average in terms of efficiency. The pump is claimed to turnover around 3500lph, and using an airflow meter, we can see that our unit draws around 500 litres of air per hour under normal operation. Whatever the actual performance, the pump on our unit is very quiet. Actually, even with the additional feed pump running it is the quietest skimmer we’ve owned. This perhaps results from the new lubrication system (a bypass system which cools the pump by circulating water around the impeller constantly) and ROTORMIX brush impeller which are incorporated. Hydor suggests that this unit will handle a reef of up to 300gal depending on stocking density and we’d concur with that estimation, although it’s always worth going for an ‘over-rated’ unit as a preference. One other thing to note is that our unit settled-in very quickly (just 1 or 2 days) without anything other than a rinse in RO water, which was useful. One minor gripe is that it looks like it will be quite hard to clean the inside of the main chamber as the skimmer body isn’t dismantleable and the opening is too small to get ones hand completely inside. Some kind of brush may help but it may be awkward to remove calcerous growths without a lengthy soak in vinegar. Also, the placement of the feed pump inlet may necessitate the addition of a hard, angled connector to avoid kinking soft pipework, and this does increase the footprint width marginally. If you are placing the unit outside the sump, the outlet pipe will need to come over the sump edge. Sealed extension tubes make this possible but note that this may increase the headroom required. These minor comments aside, we think this is a great unit for an RRP of around £230. Take note also that there are several different sizes available… click here to view the full range (UK models are known by the first part of the model numbers shown).
So, is it more efficient than the non-recirculating skimmers we’ve used? Well, to be perfectly honest we haven’t noticed a massive difference. The unit certainly does seem to pull out a much darker skimmate than the cone skimmers we’ve used though and it seems to be much more consistent and easier to fine tune too. We’ve been using this skimmer on the digital-reefs black tank for several weeks now and it seems to be coping superbly with the current biological loading. Long-term measurements of organic nutrient levels also indicate that it is doing a great job!