Hi Cory,
The tanks many years old, although its been fish only, softy coral etc during various phases. Only for the last say 3, maybe years have I had much interest in SPS. For a while it took me a long time to learn how to keep my water OK for SPS to even survive, up till about 2 years ago. I had a phase about 2 years ago to 1 year ago while I had a bit of success, bit of SPS growth and a little corraline. Then the tank crashed and I have not spent much time on it for the last year. So I would have had organics for the entire period I spent trying SPS. Organics can build up pretty quick in the water too, things like algae secrete organic compounds, for instance.
I never had much success so far, but worst success since having a kid, and now our lifestyles keep us in the house more with businesses run from home. So CO2 will have been higher during the period I had the least success. But thats not to say its the reason, could just be coincidence. That said, I am reading a lot about low pH being associated with high CO2 from people, and well sealed houses. Its only the last week or two that I realised I was probably a victim of high pH too, although that dosent mean its the reason for my failure so far. I did the pH test with my water and had a big difference in pH (ie high CO2).
Same skimmer btw yes. Re light, I dont believe now myself light is that important (or exact wavelength is important). The biological processes AFAIK do not require an exact wavelength but as long as a photon is high enough energy (ie close enough to violet), it will fuel the reactions of photosynthesis etc. I used to obsess about getting a smooth black body spectrum like sunlight but I dont now. Look at the success people have with spectrally spikey halides and LEDs for reasons a smooth spectrum is not required. Plus look at the success people have with all sorts of light and I think it seems that corals et al will grow well under many different lights of different spectrums. Pure red would not be good I suspect, but white or bluish white seems fine, and AFAIK scientifically that makes sense (but stand to be corrected if someone can point out contradicting info). Fancy lights are mostly for our entertainment IMO.
My corraline also slowly lost colour till it went white and I assume died over many months, initially. When I started getting a bit of success, it stayed the same colour on new bits. So I think corraline going lighter is a bad sign myself (was for me). Whats your nitrate and phosphate? They do need to be quite low I understand. When I had success with softies I think my water was not that clean, when I got into vodka dosing, softies slowly reduced in size over months to nothing. So I guess now that I starved them out. There was zero nuisance algae though! But it seems that people can have softies with coraline growth so there must be a middle ground between starving your softies and flooding your coraline with nitrate / phosphate.
Anyway I come back to calcification. I have very slowly learnt the details of calcification and its not something I ever really got control / understanding of before. I had best coraline growth when I used kalk as top off. When I moved away from it, looking back, my coraline started going downhill at that point. But I used 2 part so I thought I was fine (IE I was taking care of calcium and alk, but not pH, which kalk does). During the period I used kalk I had my best success with coraline although still not great, but I didnt have much evaporation either, so not much OH going into the water (to bring the pH up).
Now, I have finally learnt enough about carbonate / pH etc to begin to understand it. Because I dont want to raise my alk too much, I am wondering about removing CO2 to raise pH. If you were OK with high alk, or you have a lot of SPS or coraline (ie lots of calcification), you could either dose kalk if you have lots of evaporation, or dose 2 part with the sodium (bi)carbonate being replaced with sodium hydroxide. That would raise pH and alk together, and as CO2 is absorbed from the air, your pH drops again and all you are left with is raised alk. If you have corals taking that alk you are OK, but if like me you dont, you are stuck with high alk, and your pH still ends up low again after a few days. So the only other way to raise pH without raising alk is to remove CO2. Randy took me through all this over the last few days in several current threads, you can find them and get the details straight from him, I am sure he explains better than me.
The long and the short is that I am going to try a CO2 scrubber in the hood of the tank. If I just run the skimmer intake through a CO2 scrubber, that will still leave the tank water surface as an area that it can absorb CO2 from. So while the skimmer is removing CO2 with its CO2 free air, the tank is sucking CO2 from the room air. If I seal off the room air with a hood over the tank, and put a scrubber in that to remove the CO2 from the air in it, it should suck the CO2 from the tank, keeping the alk the same, but raising the pH, which will force calcification. As the tank animals and bacteria metabolise they will create more CO2 which will hopefully be released via the large surface area of the tank and absorbed by the scrubber.
For reasons of gas exchange and the rate at which the CO2 laden air is processed, I calculate that you need thousands of liters of air per hour going through the scrubber rather than hundreds as you get with a skimmer, which is why I believe this would be more effective than a skimmer scrubber. But my calculations or assumptions might very well be wrong. Doing this with an air stone etc would not work well IMO. But a scrubber with a small fan will pass thousands of liters per hour so would be effective. BTW this is to do with the fact that to keep CO2 at such a small level you need to process the air fast. I can explain if you want but its probably not necessary.
So either kalk, hydroxide based 2 part, or a high flow scrubber might be the solutions, and the only solution for low calcification tanks AFAIK is the scrubber, which need not be complicated I think, it means having a hood on the tank, and inside the hood, a bit of pipe with a fan at one end, packed with sofnolime (or I will try a diy solution, builders lime, as its 15 times cheaper as I detailed in another thread). Or maybe even just a tray of sofnolime in the hood would work, specially with a little fan to circulate the air in the hood well. Ive read other thread where people try to use airstones for this but physics just dont seem to work out for me, and they didnt seem to get success.
Phew long post. Sorry!
