So, all this information is very interesting. The problem is really how useful it is. One of the problems is the differences between systems. Just as example if the system run activated carbon, allelopathy would be less likely to occur. It could be even more complicated if one take in consideration the type of activated carbon that is being used. Other variables would include how old (and stablished or mature) the systems are, what is the mass of corals (which will also consume nutrients) present in the tank, fish numbers, clean-up crew, light source and cycle, etc... Don't take me wrong, I love the biology of it, and I always learn a lot, but for each answer or experience shared, there are so many questions I want to ask so I know other factors that may play a role on the success/failure of the experience.
In my case a 8 to 9 month old system, net 400 gal (total ~ 500 gal), dosing vinegar. Two display tanks connected to the same sump, one 125 bare bottom fish only (large snow flake eel, three medium fish ~ 4 inch, and a few small fish) I feed 4 frozen cubes/day (brine, blood worms, mysis shrimp, etc) and about twice that (for the snow flake eel) every 3 days; the second tank 300 gal, about 2 inch sand, SPS dominated (over 100 different corals), most small colonies (1-3 inches), seven larger colonies (5+ inches), approximately 20 small fishes and 5 medium tangs (3 yellow tangs, and 2 purple tangs) that I feed daily with 2 frozen cubes (variable) and dry food. The 125 gal uses LED (2x Radion gen 3 about 5 hours peak at 100% with full spectrum and 14 hours total, starting and ending at 3% royal blue) and the 300 gall uses t5 (2 fixtures of 8x54w, mostly blues with one close to 12,000K and one actinic in each fixture). I run 1/3 of the recommended amount of BRS ROX carbon, passively (change every 15 days).
What is interesting is that the algae growth in both system was very different. Was it the flow? Was it the fish? Was it the light?
About 5 months ago I decided stop measuring NO3 and PO4. I was only getting 0.00 measurements when there was clearly nutrients in the water based on how fast film algae was growing in the glass (I had to clean every other day in the 300 gal and once every 4-5 days in the 125 gal). Now, the film algae growth changed, I only clean the glass once every 5 to 6 days on the 300 gal and on the 125 gal. Why the change? More coral mass (increased a lot either by addition of new coral and by growing)? T5 lights are getting weaker? Just overall more stablished/mature tank?
As I usually tell friends that keep SPS, If coral have good PE, colors are good, and they are growing (or at least most of them, ;-)), I try to not change anything. I know... It always look like there is a way to improve our systems... But for me, this hobby thought how NOT TO react, because every time I did, I caused more harm than good.
