From Nutrient Export to Nutrient Management
As my replacement tank is getting ready, I started planning the filtration system of the aquarium. I was a subscriber of high inport, high export strategy, firmly believe in providing as much food as possible to the aquarium, while removing as much nutrient from water as possible through different techniques.
I had some measure of success using Nitraguard Biocubes. They are a form of solid carbon, and are effective in removing nitrates through bacteria growth and skimming. However, they are less effective at removing phosphates. Thus I use FM Ultraphos, aluminium oxide based phosphate media is much cheaper and easier to implement.
In my experience, a filtration system fully driven by carbon dosing are fairly prone to imbalance. Thus I decided to include chaetomorpha to shoulder half of the export duty. I do not like to have light spill in my sump, thus I opt for an AquaExcel Macroalgae Reactor.
Effective is an understatement.
The nitrate and phosphate are stablised at almost undetectable level very quickly. On one hand, lots of pellets and coral food are added into the aquarium on a daily basis; on the other hand, the skimmer pulls out copious, dark skimmate. The small handful of chaeto quadriple in size after one month.
As I pull out the lumps of chaeto to throw away, an idea clicked.
What am I really growing? Chaeto and skimmates or coral and fishes ? In another word, if most of the fish and coral food (expensive) end up becoming chaeto and skimmates, is it a sensible proposition? Is there a better way?
Enter the Zeolite
If improving the efficiency of nutrient management is the goal, Zeolites are a god send. These stones selectively absorbs some nitrogenous compounds, stripping them from the water column and prevents formation of nitrates. But they are much more than a nitrogen sponge. The rocks also provide numerous surface for bacteria to grow. That's not all, through the regular rinsing of the zeolites, the bacteria flocks are dislodged to be skimmed out, or even better, to feed the corals.
Now how is this different from biopellet reactors? Don't they also make use of bacteria plankton to export nutrients? There is a huge difference! Carbon dosing export nitrate and phosphate by adding carbon source, while the zeolite system recycles the dissolved C, N and P and fix them into living biomass, effectively reduce the free nutrient in the water.
In a normal aquarium, if 10% of food is used by livestock, 90% is exported as waste. In a zeolite system, that 90% is recycled, fed back to the display tank repeatedly. It's not hard to imagine how this can massively increase the utility of the food fed.
In essence, ULNS is a by product. The gem of a zeolite bases system is the efficiency of feeding, as well as the continoued presence of food for corals.