I just started with Phyto-Feast. I saw it at MACNA. It looked pretty interesting. All Things Fishy began to carry it. I use the boost for gut packing the baby brine that I feed my bangai cardinal babies. I also use the phyto-feast for my clams. It is MUCH more dense than DT's, so if you find it or use it, cut down to 1/3 of what you would use for DTs.
I tried the switch because I found that 2 out of every 3 bottles of DT that I got was already "passe compose". Even those that weren't bad, turned funky within a week or so after opening. So far, so good with the Phyto-feast. No nasty smell and the clams are not "coughing" when I use it, like they did with other dead plankton products.