After reading all of the articles, posts, and anything else I could find on the topic I decided to try silicate dosing on my 75 gallon reef. I read Randy's article particularly closely, confirmed the normal concentration range for ocean silicate through multiple sources, and purchased sodium silicate from the Science Direct site that Randy linked to. I then performed all of my calculations and test dosed a 10 gallon macro algae tank to ensure that my calculations were correct. Within that tank I achieved a silicate concentration of just below 1 ppm confirmed by a serra test kit 6 hours after dosing. Silicate fell to undetectable levels over the course of 3 days. I repeated the dose and had the same rate of uptake, saw no ill effects on the macro algae, pods, or mushroom corals present. I saw a small increase in growth on my glass that I confirmed by microscopy to have an increased proportion of diatoms compared to pre-dosing glass scraping samples.
Feeling I had done my due diligence I decided to go ahead with dosing the tank. I confirmed 0 silicates prior to starting and sampled my glass finding few diatoms. I added my calculated dose and tested the next morning. My silicate concentration was only 0.5 ppm, less than expected but I attributed that to a combination of a conservative rounding error in calculating system water volume and possibly more rapid uptake in a more nutrient rich tank. After 4 days silicate levels had decreased to undetectable and all of the organisms appeared fine except for a tiny amount of bleaching on one of the tips of my montipora digitata. I confirmed increased diatom growth and was very pleased. I thought the bleached tip might be related to fish damage or having recently gotten a little behind on top off and had hurriedly added 2.5 gallons of cold top off water the day before. I dosed the tank again. When I returned from work today the montipora was completely bleached! The other montipora frags have some patchy bleaching but have not gone completely. I performed water testing and found the following.
Temp 79
salinity 1.026
pH 7.9
calcium 400
alk 8 dKh
silica 0.5 ppm
nitrate 0
phosphate 0
I am preparing to do a water change and have an extra purigen pouch I can put in the sump. I also have an emergency polyfilter pad that I could use. What are anyone's thoughts? Is this bleaching likely related to silica dosing? Should I have started slower? The only other unusual changes for my tank were the large top off, I missed feeding the tank the night before, and I am about a week late on my bimonthly 10% water change. The tank has overall been healthy with a mild hair algae problem and good coral growth for a mixed reef of mostly LPS, softies, and zooanthids. Montipora is my only SPS. The only other coral having problems is a fungia that got damaged by too much flow and has been struggling for a month or two to recover. I was dosing silica to hopefully boost pod growth and suppress the hair algae. Could the growth of diatoms have dropped my nutrient levels too quickly for the montipora to adjust to? Would there be any point in using the polyfilter pad? Any advice for salvaging the coral?
Feeling I had done my due diligence I decided to go ahead with dosing the tank. I confirmed 0 silicates prior to starting and sampled my glass finding few diatoms. I added my calculated dose and tested the next morning. My silicate concentration was only 0.5 ppm, less than expected but I attributed that to a combination of a conservative rounding error in calculating system water volume and possibly more rapid uptake in a more nutrient rich tank. After 4 days silicate levels had decreased to undetectable and all of the organisms appeared fine except for a tiny amount of bleaching on one of the tips of my montipora digitata. I confirmed increased diatom growth and was very pleased. I thought the bleached tip might be related to fish damage or having recently gotten a little behind on top off and had hurriedly added 2.5 gallons of cold top off water the day before. I dosed the tank again. When I returned from work today the montipora was completely bleached! The other montipora frags have some patchy bleaching but have not gone completely. I performed water testing and found the following.
Temp 79
salinity 1.026
pH 7.9
calcium 400
alk 8 dKh
silica 0.5 ppm
nitrate 0
phosphate 0
I am preparing to do a water change and have an extra purigen pouch I can put in the sump. I also have an emergency polyfilter pad that I could use. What are anyone's thoughts? Is this bleaching likely related to silica dosing? Should I have started slower? The only other unusual changes for my tank were the large top off, I missed feeding the tank the night before, and I am about a week late on my bimonthly 10% water change. The tank has overall been healthy with a mild hair algae problem and good coral growth for a mixed reef of mostly LPS, softies, and zooanthids. Montipora is my only SPS. The only other coral having problems is a fungia that got damaged by too much flow and has been struggling for a month or two to recover. I was dosing silica to hopefully boost pod growth and suppress the hair algae. Could the growth of diatoms have dropped my nutrient levels too quickly for the montipora to adjust to? Would there be any point in using the polyfilter pad? Any advice for salvaging the coral?