Now i see it.
I have used this in fluidizes sand filters with BIO PEARLS From UK' s TMC ( tropical Marine Center )
I gave up because the pearls get consumed very quickly ( i know heavy load ) and are very expensive in here and, secondly, because the fluized cannisters all had a fault and got holes in their bottom through the constant scrubbing of the pearls or sand.
What i never noticed, with my system, is that increase of mud/slime you mention. Why is that? My water passed through the pearls directly into the sump...
Crud... I hate it when that happens. I had a nice well crafted reply, hit post (or thought I did) and lost it. I'll try again.
The "slime" I continually reference is actually bacteria (probably bacillus). Think of this as a planted tank. Plants consume nitrogenous waste from the water, storing it in their leaves and stems. But this waste (ammonia and nitrate) is not removed from the tank until the plant is pruned and it's leaves and stems are removed. Otherwise, if the plant dies, or leaves break off and are not removed, then the nitrogenous waste it has stored is released back into the water as the plant decays.
The same concept is at work here except we are using bacteria instead of plants. Bacteria populates the bio pellets while using them as the needed organic carbon source. As the bacteria consume nitrate and phosophate from the water, they divide, growing in population. Excess populations split off from the pellets looking for a new home. This excess bacteria is the "brown slime" that is being harvested by the mechanical filtration. If not captured by mechanical filtration (or protein skimming in a salt water tank), they land wherever, die (no organic carbon source to be utilized as a source of energy), and degrade, releasing the nitrates (and phosphates) they had stored back into the water. In your prior use of bio pellets, if you were not harvesting the resulting bacteria, you probably did not see much of a result.
In response to your other concern, I don't want to sound like a sale weenie from Dr. Tim's, but I went with Dr. Tim's because his pellets are manufactured specifically for the aquarium hobby using 100% PHA, no other ingredients. Other pellets are likely manufactured for a different reason and re-purposed for the hobby, containing an unknown level of impurities and other compounds that are water soluble. These type of pellets would be subject to quick degradation while pure PHA will only be degraded by the bacterial processes we are seeking to cultivate. I am on my 5th week of using Dr. Tim's NP-Active Pearls, 3rd week of nitrate reduction, 2nd week of basically running near zero nitrates, and have not noticed a decrease in pellet size. I am expecting to receive 3-6 months of nitrate reduction using $35 worth of pellets on 120 gallons of water. If that changes, I will certainly update this thread with that information.
I am using an inexpensive Phospban reactor. While I would rather have one of the monster pellet bashers, the Phosban reactor is working out well enough. There is a strainer plate between the pellets and the bottom of the reactor. I'll keep an eye on that plate to see how well it lasts.
