First time I have heard this - any links? It is interesting because I thought that nitrogen fixation only can take place in anaerobic compartments and they are hardly to find near photosynthetic corals (corals with zoox) Would love to see these links.Corals are very efficient at recycling nitrogen and have simbiotic diazotrophs that can convert N2 or free nitrogen into nitrates if needed
I have seen this article before and i don't really know what I should think about it - they report this and this is in NO3 concentrations below 1 ppm NO3. And after that I look at my aquarium that runs at 6 ppm the last month - and I see thisI'm not surprised at all. Reef ecosystems are very complex and there's A TON MORE going on than just nitrates and phosphates. Nilsen and Fossa's "The Reef Aquarium" Vol 1 documents pretty much what you've seen in your system. My own experiences also echo the decline of algae with nitrate and phosphate staying stable or increasing. If it was my tank I would not be dosing other than to keep phosphate above .03 mg/l. Corals are very efficient at recycling nitrogen and have simbiotic diazotrophs that can convert N2 or free nitrogen into nitrates if needed. You should also be aware sponges and biofilms (and just about everything else) are messing with nitrogen and phosphates and can be manipulating the numbers showing up on test kits just like corals and algae do. ANd be aware dosing nitrates might make corals more colorful but research has shown it has a more severe negative impact on calcification than phosphate. Here's fig. 3 from Shantz and Burkpile's review of almost 4 dozen research papers:
Sincerely Lasse