Chasing parameters never healthy...
EDITORIAL
The notion of “don’t chase parameters” is not new and like many generalities has merit. Staying within recommended parameter ranges for reef systems is a more explicit version of this idea. In other words, kicking a ball anywhere between the goal posts is just as good as in the dead center. However, we tend to deviate from this recommendation when discussing “cures” for nuisance organism growth. When cyanobacteria or some pesky macro alga appears, nitrate and phosphate take on special importance and the notion of staying within the ranges seems to be forgotten.
Stay within the nutrient range and cyanobacteria mats do not form (cyanobacteria are very likely growing in every system all the time, but mat formation is the event that draws our attention). Stray from a rigorous discipline of nitrate control and bang, red slime mats appear. In reality, the connection is not so black and white. Cyanobacteria mats can appear under high nitrate/low phosphate, low nitrate/high phosphate, high nitrate/high phosphate, and low nitrate/low phosphate conditions. What’s going on?
First consider that we treat our aquarium like a chemistry set. Our diagnostic tools are temperature, pH, salinity, chemical test kits. Is it any wonder that we try to explain or relate every problem to chemistry and come up with solutions that have variable success rates? What about adding an ecology perspective to our diagnostic tools?
We typically have to deal with benthic (surface) pests rather than pelagic (floating) pests. And how do we diagnose the problem? By sampling the water and testing. Not because there is a solid link between what we measure in the water and the growth of the nuisance organism but because that is what we can measure. Adding to this diagnosis problem is the fact that much of the scientific fact we use to explore and explain issues come from studies in the ocean of distantly related organisms. Much of the scientific fact used in cyanobacteria discussions comes from studies of pelagic species in the ocean and in lakes. While using analogy is not “wrong”, it can and does have limits in explanatory power. We rarely stop to think about the conditions 1 mm above the surface where our problem exists. The notion of ensuring high flow at surfaces and “blowing off detritus” from surfaces are examples where aquarists are thinking at the appropriate scale in dealing with nisance organism growth.
Finally, nuisance organisms need just so much food to grow at their maximum rate. Any additional amount does nothing to increase how fast they grow. That number is unfortunately low. For macro algae, they hit their top growth rate near the lower limit of what we can measure for nitrate and phosphate.
The take home message is that dealing with nuisance organism growth is difficult and likely to take awhile to fix. Analytical chemistry results can play a supportive role, but unlikely to answer the question “why is it growing”. And without that answer, stopping the growth usually means trying multiple “cures”.
