[plancton]

Like redfishsc pointed out, it could be possible that dinos were feeding on larger components such as detrius, that would explain why the removal of the sandbed helped a lot.

I don´t know if they are feeding on trace element on the salt but there is a direct relation of them dying when small nitrate concentrations.

For example last time they started to die when nitrates were 2 ppm, they have been thriving this month in low quantities and my reading showed 0 nitrates last week, however this week I´ve seen them starting to die again, I suspect the nitrates are rising again. After a water change nitrates do drop to 0, and this is very possible since for example 2.5 ppm is a very low nitrate reading, besides the reading might not be necessarely 0, but just below 2ppm which is the minimium measure in most test kits.

I didn´t know Sprung also mentioned not doing water changes.

Oh and there´s another evidence that the sudden slow decline this week on the dino population might have to do with nitrates rising:

Monti caps are coloring up again, long time ago, basically since I set up my tank, I noticed that monti caps broght from other tanks were losing their colors in my tank, where the nitrates were 0.

My LFS said he came to the conclusion long time ago that monti caps need low nutrient levels 2-3 ppm to have good coloration, this phenomenon might be related only to monti caps, and these low nutrients don´t seem to be affecting the other corals´coloration.

So a month ago before the last water change, nitrates were 2.5 ppm and the monti caps were fully colored, the week after the water change they became very pale and now they are starting to gain color again after a month at the same time that dinos are starting to decline.

I will be creating another topic related to this coloration on low nutrient levels with a picture of the monti cap at 0 ppm nitrate compared to 2-3 ppm nitrate.

BTW. I don´t recommend directly dosing nitrate, don´t know what could happen, just let the tank get dirty on its own.