We have done a number of phoslock applications over the last four years. Alot of discussion about alum but in our area (coastal SC) our waters are soft and alum is usually not a candidate. In one case we had a 2 acre lagoon 15+ years old, routine HAB boom and bust blooms and finally a fish kill (even with aeration). After testing phosphorous levels we did a complete reset, or attempted to remove all the phosphorous. We've had no HABs or treated algae in 4 years. Note this was not managed for fish but for aesthetics. Have also done partial phosphorous removal to reduce fertility. Yes phoslock is expensive but it works. Invest in proper water chemistry tests.
I'd like to throw some info in on this as Phoslock is one of the products I looked at when I started my research. I have the MSDS sheet for this product which until recently, was available to view, now it just says "proprietary" ingredients.
The reason this product doesn't work well in soft water conditions is because the buffering agent is Sodium Carbonate-zero effect on hardness because it has zero Calcium.
Thanks to Rainman, (Rex), I researched this until my eyes wouldn't work. I dug hard because Rex said to use Hydrated Lime instead of Sodium Carbonate (soda ash). I wanted to use soda ash because we had a pallet of it. I just needed to find the answer as to why Rex said Hydrated Lime only.. The reason is the hydrated lime is loaded with calcium. Not only is it a good buffer for acidic reactions of Alum, it brings the alkalinity up (increase hardness).
Phoslock can't (won't) do that.
