Other methods of removing PO₄ exist but non of them are suitable for aquaculture. For example, Alum is used to remove PO₄ in numerous applications but can not be used effectively in aquaculture because 1) it produces flocs which settle and clear the water which is a result we do not want and 2) it is an aluminium compound so is not suitable for aquaculture. A detailed comparison of Alum with Phoslock is presented here. Other phosphate removal agents include iron compounds. These are useful in waste water applications where processes can be put in place to remove the precipitates. In aquaculture no such processes can be economically employed, so the precipitates will sink to the pond bottom where biological activity will lead to the re-release of the phosphates. Phoslock differs from all these products in that it is safe to the aquatic environment and the binding of the PO₄ by the active ingredient of Phoslock, lanthanum, is permanent.