NP-Biopellets, the story so far

It is often thought that one of the main reasons for our inability to keep many of the more delicate denizens of coral reefs is the lack of available (or acceptable) food. Back in spring 2009 I decided to see how far I could push feeding using a good quality skimmer (ATB Medium/1050A 1.5) and DOC dosing and still maintain reasonably good water quality. As expected, I eventually reached a rate of nutrient input that even my extreme DOC dosing couldn’t handle. At this point I was dosing 25 ml vodka plus 10 grams of sugar per day and yet I I still had measurable nitrate and phosphate. I started to notice many classical DOC dosing problems (corals loosing pigmentation, visible bacterial growths, restricted water flow in pipes and hoses etc). Thus I had only a couple of choices: I could either reduce feeding or add more and/or bigger technical equipment. For various reasons neither was attractive option for me.

After an ill-judged experiment with Tropic Marin BioActif (an experiment that left me with 25+ ppm NO3 and 1.0+ ppm PO4) I found an article (“Filter and suspension feeders” at coralscience.org) that mentioned a new form of filtration that made a lot of sense to me: a solid source of labile organic carbon that would release carbon only through enzymatic action of bacteria. This means two things: first of all, it makes overdosing pretty much impossible and secondly it avoids most of the problems that results from heavy use of DOC.

The old 2 liter setup. Pellets were quickly clogged with bacterial biomass.

I started out with only one liter of NP-reducing BioPellets (NPBs). Considering the “bioload” this was clearly too small amount for my tank but for once I wanted to be cautious. Seeing that nothing died and that the pellets were quickly colonized by bacteria (product was not available in stores at this time and there were no user reports) I added a second liter of NPBs. This was the recommended amount for the size of aquarium I have but considering my quite unorthodox feeding regime I didn’t stop the dissolved carbon dosing completely but cut it to half instead. With this combination of solid and dissolved organic carbon the nutrient levels stayed pretty much the same as they were with twice as high DOC dosing. So obviously the NBPs were working as advertised and I had reached my goal which was not to stop DOC dosing completely but to reduce it to more sensible level.

After a couple of months I still had some measurable nitrate (2.5 ppm) and phosphate (0.04 ppm) and I decided to really go “overboard” and ordered 3 more liters of NPBs. Since I didn’t have large enough “reactor” for this amount of NPBs I made a simple open top canister filter from an old 10 liter GAC container and a small 1000 l/h pump and placed the 5 liters of media in there. At the same time I stopped DOC dosing completely.

5 liters of NP-Biopellets in a 10 liter bucket. Using modest (1000 l/h) pump and large diameter container results in slow water velocity which seems to give best results in my case.

The results have been wonderful. It seems that the “critical mass” for my aquarium was around 5 liters of NPBs. The water stays crystal clear at all times and nitrates are finally dropping below 1 ppm. Using many commercial foods with excess phosphorous I still must use small amounts of GFO (before NPBs 2000 ml and now about 500 ml). I feed about 3-4 grams (dry weight) of pulverized invertebrate foods daily which is equal to about one 500 ml bottle of commercial liquid invertebrate food.

My NPBs used to get clogged pretty fast with thick bacterial growth but now, with twice as much surface area for them to colonize, the need to stir the media has diminished significantly. This might actually be a good indicator for sufficient amount of NPBs: if you find your media clogging very fast you might need more pellets to increase the usable surface area. Of course nitrate concentration is also a good indicator.

Comparison of costs of different filtration methods. Assuming 4 x 54W T5 lighting, 18 hrs/day. Bulb replacement every 9 months, 30% of NPBs yearly

I would recommend NPBs to all reef aquarists who are feeding their tank with invertebrate foods. Don’t be afraid to use more than recommended by the manufacturer. All tanks are different and manufacturers can only make general recommendations. Although the cost might seem high at first glance, NPBs are still a lot cheaper (and easier) than maintaining a large enough refugium to match the nutrient binding capacity of NPBs. Electricity and replacement bulbs aren’t cheap! There are also some competing products coming to market so I would expect the price to drop.

Tags: equipment, Husbandry, nutrients, tank

This entry was posted on Monday, February 8th, 2010 at 20:21 and is filed under Husbandry, Ideas and misc. You can follow any responses to this entry through the RSS 2.0 feed.