All of Sanco's bacteria is formulated to consume organic material, muck or sludge.  Our liquid bacteria is simply a maintenance dose.  The water soluble bags are more concentrated and will break down and consume the muck faster than the liquid.  The spikes are the most concentrated.  The spike design is also beneficial because the weight and shape of the spike will insert itself deep into the muck.  The spikes are recommended for recreational areas that have become unusable due to muck build up.