Just found this and guess what I added back in like Nov. guess where most of my cyano
and green hair algae is growing? added 50lbs
"Rocks and substrate
Dead reef rock (also referred to as base rock), tufa rock, but also crushed coral substrate may contain serious amounts of phosphates. Some is bound very tight (pretty dissoluble minerals), some may be dissolved given the proper biochemical environment. If you want to know approximately how much soluble phosphate is contained in a specific rock or substrate, it is possible to test it in a bucket with heated and moved salt water for some days. Contents of 1 mg
phosphate per kilogram of rock or crushed coral, and higher have been determined that way. A tank in which such rock is used will have high phosphate concentrations for a long time. If phosphate rich rock material is already in your system, there are two possible solutions: Take out the rocks, or increase the phosphate output of your system (see below).
The use of dead reef rock may be seen as one of the major sources of long term high phosphates in marine aquariums. If they are used they should be rinsed very well. Dead reef rock should also be scrubbed. Proper bleaching may be necessary to remove some of the more soluble phosphate containing agglomerations and minerals. Fresh and cured life rock, however, has a much lower phosphate content and should be preferred when setting up a new tank. "
by Marco Lichtenberger