[IslandCrow]

What type of plankton are you using. If it's DTs, what it says on the bottle is true. When you first open the bottle, it will smell really bad. If it continues to smell like that after a few seconds, it's gone bad. Otherwise, you should be good. If you're making your own phyto, it has almost a sweet smell when it's fresh. When it starts smelling even a little bit like rotten eggs, it's going bad. It's probably not completely bad at that point, but as long as you refrigerate it and give it a good shake every couple of days, it should be at least a month or two before it starts smelling bad.