Originally Posted by earlysteven
Really I've always heard great reviews on both of them is this personal experience ?
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Purple up is nothing but calcium, iodine, and some trace elements. Regular weekly 10% water changes is more than enough to supplement everything that's added by purple up. If your tank is consuming more calcium and alkalinity than water changes are adding then the purple up will never make up the difference. You would be much better off doing a 2 part dosing at that point.
Beyond that, I've seen many people here on the forums have problems when supplementing with the purple up that went away when they were told to stop using it. Coincidence? Possibly, but imho
water changes will always be far better for your tank. Ive never used it personally, but its commonly used among newcomers to the hobby and is avoided by the experienced reefers.
As for the bottled phyto, I did use it for a while until I started my own phytoplankton culture. When it's not refrigerated phytoplankton doesn't live for a terribly long time, and is good for at most 2 to 3 months. Bottled phytoplankton is all dead and just extra nutrients to throw in your tank.