Koi ponds particle dynamics Part 2
Why is it important that the solid wastes are not broken up?
Particle dynamics tells us that the smaller the particle, the lesser the effect it's density plays on it's ability to settle out. If our lead particles were small enough, and there was enough water movement in the pond, these particles would effectively remain in suspension.
Solids in suspension can' be a good thing. Common sense tells me that it will be much harder to get suspended solids down to the bottom drains, and that the chances of these particles collecting elsewhere in the pond unbeknownst to me are consequently much higher. For instance, they might become trapped in the algae of the sides of the pond. There they will rot and pollute my water.
If the particles are small enough they may actually float up to the surface. They may collect together and become trapped in clumps of floating gunge and if I don't have a surface skimmer, there is a potential problem that can quickly develop. I don't want this in my pond, so a surface skimmer is an essential item - it's not there to catch leaves although that is a welcome bonus - it is there to catch SOLID WASTES that the bottom drain does not!
By no means discount the bottom drains performance! It will account for the vast majority of solid wastes if it is designed and installed correctly. Sloped bottom weirs and careful positioning of return jets will encourage solid wastes to be channelled to the bottom drains as fast as possible. The faster they reach the bottom drains, the less chance there is of breaking them up and the less the probability of any solids being stuck to the sides of the walls of the pond or anywhere else for that matter.
I touched on something earlier - the issue of significance. How much solid material that sticks to the side walls or collects around the pond is enough to be of significance? This is a question I can't answer. It depends on the size of the pond. It depends of the capacity of the biofilter. It depends on the efficiency of the mechanical filtration system. It depends on the number of Koi. It depends on the temperature of the water. It depends on what the Koi have been fed and in what condition they are in. It depends on what pathogens are present in the water already.
What I can say without hesitation is that problems that develop in Koi ponds are the culmination of a series of events. For instance, if we have a Koi pond that has mechanical filter that becomes blocked or is not cleaned after some time. Some heterotrophic breakdown at this stage starts to increase the load on the bio filter. It's a warm summer day and the Koi keeper decides to feed his Koi three times instead of the usual two. And he decides to increase the protein intake to grow his Koi faster. And he's just added three new big Koi to his collection a week ago. And his waterfall pump seizes just after the evening feeding session. And somehow he manages to increase the throughput through his filtration system to try and compensate.
Your guess is as good as mine but I would suggest that the Koi asphyxiate. The increased solids loading on the filter system that now pulls water through faster, breaking up more solids than before - meaning more solids in smaller particles get fed back into the pond without being removed - sticking to the sides and providing bacteria with more food to break down - a process that consumes oxygen and provides food for an algae bloom that further robs oxygen - sending the entire pond in an oxygen deprived situation - under warm water circumstances.
Who takes the blame? The waterfall pump of course!
So, what is a significant amount / percentage of solid waste in a Koi pond? The answer is that it depends.
If the question is altered to how much solid waste in a Koi pond can be considered as safe, then the answer is much easier. A zero solids reading will be safe. Impossible to attain, yes, but the closer you get the safer you are.