Hey Plantbrain,
Wish I had come across this thread sooner - I recently just siphoned out approx 2-3 liters of crushed coral from the bottom of my 200 liter tank. I've setup a Refuge with something kinda like Southdown, and also used the same sand in my main tank as well.
From the Crushed Coral, I used my wifes strainer (she loved that idea!) to seperate the CC from all the "life" (pods, worms, etc.) as I wanted to put this back in my main tank & refuge.
I couldn't get all the life seperated from I think was really fluidy mud type substance. When I seperated this "mud" from the clear water (once it all had settled), I had about 3-4 cups of this "mud". Not able to seperate all the life from this mud, and concerned that this mud might be more like a "nutrient bomb" if I put it all back in the tank, I settled on a comprimise. I figured the 40-50 kilograms of LR I had would already contain enough "life" to thoroughly populate the tank with more pods, worms, seastars, etc. - I opted to about a cup of the "mud" back in the refuge. This also was a hedging of my bet, as it's easier to break down my 45 liter refuge than my whole tank to clean it out if I had ended up making a mistake I needed to back out of.
I didn't mix in this "mud" with the sand - it's just kinda loosely laying on the top of the sand, but the gentle currents in the refuge have gradually cleared off some parts of the sand & collected the "mud" in other parts of the refuge.
I also have about 2 handfuls of Caulerpa Prolifera growing in the tank, and some thing that I think *might* be spaghetti macro, but not quite sure.
So what do you think? Is this type of "mud" I gathered, kinda like the mulm you are talking about seeding refuges with?
Or did I make a grave mistake?
BTW, I checked my water a couple of days after all this, and my Nitrates have shot up to above 50ppm, but my Nitrites & Ammon & everything else appears to be perfect. I'm mixing 30 liters up now to do a water change to take care Nitrates, as I expect this is from all the "nutrients" I stired back into the water changing the CC out for sand.
-> Kev