Can silicates in aquarium water be removed by adding a filter to the sump? I didn't have this problem for 7 years, nothing has changed that I can recall.
My NO3- 33.4ppm and PO4- 0.178ppm hasn't changed in 3 years.
Hmmmm, actually it's a certanty a lot has changed. My experiences over the last 4 decades clearly showed to me reef systems are very dynamic and there's a lot more is goining on than what we can test for.
This study showed even with a tightly monitored system microbial stuff is all over the place. Ideally knowing how much change there was day to day for several months before silicate started climbing would be helpful but I don't know anybody doing that much testing. 2 things I do know is sooner or later no matter how "stable" a system may be nuisance algae of some kind can show up, maybe rarely, maybe seasonally, and manual removal works well and IMO is the best way of "resetting" a system.
Considering how long you've gone without issues it sounds like you're seeing a case of
"Old Tank Syndrome". I imagine there is something you could use to reduce silicates in your system and you can research to see what it is. But My suspicion is there's something else more systemic going on and what you need to do is larger or more consistant water changes (5% to 10% weekly) and more aggressive removal (
this is what I do). I would stop carbon dosing, there's tons of research showing increases in DOC aka carbon dosing is detrimental for corals causing issues both acute and chronic issues short term as well as over the long haul.
Here's some of the stuff on DOC:
Maintenance of Coral Reef Health (refferences at the end)
"Coral Reefs in the Microbial Seas" This video compliments Rohwer's book of the same title (Paper back is ~$20, Kindle is ~$10), both deal with the conflicting roles of the different types of DOC in reef ecosystems. While there is overlap bewteen his book and the video both have information not covered by the other and together give a broader view of the complex relationships found in reef ecosystems
Changing Seas - Mysterious Microbes
Microbial view of Coral Decline
Nitrogen cycling in hte coral holobiont
BActeria and Sponges