A question from a UK Koi forum about blanket weed and why is it gone now without chemicals?

A week back I noticed I had the beginnings of a blanket weed problem I had strings of it forming in the main pond over 3 inches long and one area around the anoxic baskets things were looking quite clogged with matts of the stuff forming. I thought I had better get the CBA in before things got out of hand.

I have been struggling all week with piles of grot in the cetus sieve - if you don't clear it out at least once a day it blocks the sieve up - its not the green slimy stuff I had last year after treating with CBA but blackish and more granular. Today I looked in the pond and the blanket weed is gone. Well done CBA I here you say - BUT the thing is, I never actually got round to dosing it - It went all by itself!

Any ideas why? Anyone else had this happen?

Okay, I’m going to give you some insight on the whys and how’s about the AFS and bacteria. A cyanobacterium grows in the AFS because it is one of the only bacteria’s that can take Nitrogen from the dinitrogen (N2) process directly from an aqueous solution and the atmosphere. The BCB’s through microbial facilitated processes begin to covert nitrates through denitrification processes by now making Nitrogen (N2) inside the BCB. This molecular nitrogen (N2) as it starts leaching out of the BCB’s now becomes a foodstuff for the cyanobacteria or blanket weed as you call it. This now explains why the AFS gets full of blanket weed because of N2 containment of the foodstuff that would other whys go back into the aqueous solution and/or atmosphere of our ponds if it didn’t have a containment vessel of some kind, like the box (AKA: Anoxic Filter) you built to hold the BCB’s. Those small innocuous pond pebbles or that black screen that you placed on top of the baskets now becomes a means or holding ecosystem for the cyanobacteria to consume N2 on. 

However, even when the N2 is exhausted the cyanobacteria can make its own foodstuff, so now it can become independent of the N2 being produced by the BCB’s. A conventional filter doesn’t have this capability to contain its byproducts and your pond therefore becomes its containment department. This would explain why this bacteria or blanket weed grows all over the main pond. Waterfalls become a nesting ground because cyanobacteria can take atmospheric nitrogen as a foodsource and anything else that is being expelled from the waterfall too.

Now the magic begins! The bacterium inside the BCB starts making antibodies as the weather warms up. These antibodies are not blanket weed friendly and soon little by little the blanket weed starts breaking down and dyeing. The hobbyist can physically see this, by their prefilter(s) beginning to clog up with this blanket weed that has broken apart from its holding base. There is no set rule on when this will happen or exactly at what temperature the blanket weed will dye. Depending on the parameters of the filter and/or pond the situation will be determine by the facilitating bacteria and there is really no way of speeding up this process. It’s like the same principle as Barley straw does with making hydrogen peroxide by bacteria breaking it down, but you’re using bacteria to fight another bacterium inside the AFS. Plants also do the same thing with each other, if they don’t like a plant that’s near them; they try and kill it off.

Once again this is not a perfect system because there can be more microbial producers of a byproduct than users and this then will cause an imbalance in the system. This change can happen because of excess foods with phosphates, temperature, even overcrowding of the water body with too much fish mass to water availability. Even microbial availability is subjective when it comes to an AFS and other filters. An AFS can sometimes starve a conventional filter of its foodstuff if all parameter become ideal for the trilliums of cells in the BCB’s. Adding plants to a BCB can have this same affect also by taking in ammonia directly into its cells along with eradicate some germs too. This then explains why your Bead filter medium is cleaner now than in previous years. Cells will only grow according to the available foodstuff that is presented to them in bulk water. If the available foodsource is gone then so will the bacteria vanish, too!

The three photos show before and after pictures of how cyanobacteria looks and is there one day and gone the next.