Sequestrants are included in domestic laundry detergents to tie up ions of calcium and magnesium. Although not as inhibiting as they are on soaps, these minerals found in hard water still reduce the efficiency of synthetic detergents. Sequestrants were once based on sodium tripolyphosphate, but, because this acts as a fertilizer promoting weeds and algal growth in waterways, they were replaced by sequestrants based on zeolite/sodium carbonate/polycarboxylate.