Sand filters & Sludge kills so take care of your pond filter better

My original page on sand filters as part of a Koi pond filter system dealt mainly with the effects of channelling in a sand filter - and the creation of dead spots. Let's examine this a little more closely.

In a typical Koi pond the organic load of solid debris is considerable. Up to 70% of this doesn't even come from the Koi themselves! It comprises of dead algae cells, dead bacteria, plant debris, debris that has washed into the pond, dead insects, woolly mammoths and the like. So your Koi pond, even without Koi, is going to generate significant quantities of organic solid debris.
Note that solid debris that is not organic is of little concern to us. Generally it is hopefully inert and large enough to be removed manually before it becomes a problem - normally it comprises of foreign objects (Golf balls, nets, beer cans(!), metals, plastics, etc).

So now what happens with a typical sand filter system? Firstly all the bottom drains feed into a pump which takes the big solids and churns them into a fine grade soup. This is a bad design! At all times you want your pump AFTER your filtration system has done it's job so that the pump is only in contact with clean water. If this is not possible, you need to have your pump as far after the mechanical filter system as possible. This implies some kind of pseudo gravity fed high pressure combo filter system. This way you can have an initial settlement of solids via a vortex chamber and/or brush chamber BEFORE the bottom drain feed hits your pump and goes into the sand filter.

I suppose you could have a pump that 'sucks' the pond water through the sand filter but I can't imagine how this would work terribly well, especially when you try to backwash the thing.

In any event the pumping problem is a minor issue. Should your solids be churned into soup the adverse effect of this is that more will escape the sand 'trap' that the sand filter presents to these unwanted solids. In effect, these finely churned solids will simply find their way into the bio filter where the bio filter media will have to deal with them. If you manage to feed larger solids into the sand filter without churning them into a fine mush, fewer will find their way into the bio filter which is the situation that you want (no solids at all should pass into the biofilter).

Remember that there are TWO phases to filtration - mechanical to strip out the solids, and biological to strip out the dissolved wastes (mainly inorganic).

The confusion arise in that the bio filter can ALSO deal with solid wastes and break these down into smaller components to the point where they are effectively dissolved. This process takes place using heterotrophic bacteria - these are bacteria that operate in oxygen rich water and use up the oxygen in breaking down solid organics into AMMONIA and other waste by products.

Heterotrophic bacteria compete about 4 times as efficiently as the nitrifying bacteria, in the case of Koi pond filters these are the GOOD guys. This means that if you have any solid organic material getting into your biofilter, the heterotrophic bacteria take over and dominate the filter. They gobble up all the oxygen and they release copious quantities of ammonia and other noxious compounds and the poor nitrifying bacteria now not only have to deal with this additional load but they have to compete for oxygen at the same time!

Looking inside a sand filter that is efficient and traps all the solids as it should we can see that we should expect to find a seething mass of heterotrophic bacteria stuffing their proverbial stomachs full of abundant delightful organic solid food. And indeed that's exactly what we find. You also ought to be able to measure a HIGHER ammonia level leaving the filter than entering it, particularly after a good Koi feed. You should also notice a drop in oxygen level of the water - although the residence time inside a sand filter is very short.

None of these things in and of themselves is particularly bad. A good bio filter that has sufficient capacity should be able to handle an additional ammonia 'spike' as it normally does after feeding anyway. The system in essence runs at 'steady state' - what comes in goes out, albeit in a different form.

The real trouble starts when the sand filter starts to clog. Once our 'dead spots' form there is little water flow and little oxygen and massive quantities of rich food for ANAEROBIC bacteria to have a field day in breaking down these solid foods into toxic organic poison - recall the frog in article 9?

At all times the pond water is in intimate contact with whatever is happening in the sand filter. If masses of toxins are being produced, if masses of bacteria are growing and being sloughed off into the feed stream, there is no where else for these things to end up other than in the Koi pond itself. It can be argued that dilution plays a role, and that it 'toughens' the Koi up, boosting their natural defenses. At the same time, my thinking is that there is no way any pond can be kept sterile and having additional toxins and bacterial load in a pond than is already there makes absolutely no sense to me whatsoever. This is why I sought and found an Answer and why I started bringing them into the country - because the Answer removes all the solids and associated heterotrophic (and any anaerobic) bacteria from intimate contact with the pond water. Even if the solids turn into the most toxic bio hazard imaginable, this poison cannot get into the pond nearly as easily as it does via a sandfilter.

But sand filters can get away with this over time. They have big surface areas and big colonisation by heterotrophic bacteria (not necessarily a good thing) as well as some nitrifying bacteria that will be present in any event. Because the residency time is so short, only a trickle of any poisons present these poisons slowly enters the pond over time and is dissipated either by recirculation through the bio filter or by other natural means. Is this good enough?

The answer depends on you. I have a client with a smallish pond, lots of Koi and a sand filter that hasn't been cleaned in over a year. The fish are healthy, the pond is clear and what more could you ask for?

Personally I couldn't sleep at night. It's a time bomb. The filter's capacity is finite and it takes just a small thing to go wrong - say a power outage for a few hours for a complete disaster to set in. Added to the fact that the load on the filter is slowly growing over time as the fish add more wastes and fuel the growth of algae and bacteria I feel that this is a recipe with only one sure finality.

Koi Keeping ... Is Koi keeping only for the rich?

I get a lot of e-mails from people who have 'budget ponds' into which they have chucked a couple of Koi. After a short while they cannot see their Koi and they want a quick fix solution.

Believe me too when I say I have champagne tastes and a beer budget. Which is why I am writing this article.

You do NOT need to be swimming in cash to be able to keep Koi. Having money certainly helps, but it is not vital. But you do need to understand that keeping Koi does involve some money. It is a nice to have hobby, and not an investment in anything other than the pleasure of keeping Koi.

I have yet to see a Koi pond that adds value to a home that didn't have the pond in the first place. Sorry guys. If you want to add value to your home, dollar for dollar a Koi pond is about on a par with adding garden gnomes...

Keeping Koi does mean spending some money. If you want a happy Koi environment you can do so without spending vastly on filter systems of the types that we sell (we sell the very best and it unfortunately costs quite a bit). But if you understand the PRINCIPLES of good Koi keeping you can DIY quite effectively.

The principles are simple to start off with. You need to know exactly what you are doing BEFORE you begin and you need to know WHY you are doing it. If you do not have this knowledge, or are not prepared to get it, then no matter how much (or how little) money you have, all of your efforts will be wasted. I have seen first hand some very, very expensive Koi pond disasters!

But then I also see and hear of more budget pond disasters than I should. Why?

I think that the primary reasons are ignorance, bad advice and our societal culture of the new millennium - I WANT IT AND I WANT IT NOW!

The bad news is that it doesn't work when it comes to Koi. The Japanese have slaved for generations to breed stunning Koi and they know how to keep them, probably better than anyone on the planet. But they also do this full time!

Planning a pond, any size pond, is critical. Adding Koi to an existing pond is the easiest thing in the world, and also the stupidest if you haven't thought further down the line than next week. Koi after all, GROW!

My advice is to learn from others that have kept Koi before you. Preferably learn from someone who has made all the mistakes, killed a couple of Koi and eventually filled in their pond with a nice daisy bush plantation. If nothing else you will learn what doesn't work and then you can ask yourself whether the advice you've been given to do exactly the same thing is worth what you paid for it (the advice) or not!

OK, so now for the sales blurb. Actually it's not really. I purely want to save myself as much time as possible - explaining all the intricacies takes a long time!

The way I see it is that you can get 8 hours pure consultation from the world's foremost Koi keeping expert for R1495. Depending on the speed you read at (it took me 8 hours to finish both books in the set) you might even get more 'consultation'! If that R1495 doesn't save you at least that three times over, send the book back to me for a no questions asked full money refund. If I could sell the book for less I would - it's something that I consider mandatory for ANY Koi keeper, whether your tastes are champagne or beer.

And as always there's something from Hannes. I just can't seem to keep him quiet in his box in the corner. I think I need to buy a bigger stick. Hannes, sadly, has to sell Koi to eat. Hannes doesn't eat very well I might add.

His new Koi from his pre-emptive strike visit to Japan ahead of all the world's dealers are on the site here:
http://www.happykoi.co.za/koi_sales.htm

Better yet, if you want to add to Hannes' already slim line figure you can do so by joining him on his next trip to Japan in April (depart 1 April arrive back 11 April). If I can scrape together the R19800 for everything (ex food and drink, and ermm, economy class tickets - ugh - remember my tastes??!) I will be there. Why? Because you pay the price the breeder asks (plus transport, clearance and VAT to get the Koi back to SA) - and that's it. You score because of Hannes' bargining power and Hannes scores because of his increased bargaining power!

It's the best way to get your tategoi at the best price, and you get to see a little (very little) of Japan in between the rushing about between Koi breeders. You'll also see why everyone buys their Koi from Hannes - his prices are honest! You must e-mail me soonest with regard to this as Hannes only has a few places left. You will need to also cough up a R1000 non refundable deposit.

Our auction of some Koi will be happening soon. I am busy fixing the website (again- sigh) so if there is anything that bombs on you, or some font that screams at you (some have made themselves rather large - bad fonts!) please ignore them and they will be duly cut back to size shortly. So it will be happening - and we won't let you overpay for a Koi (because we're not that kind of people) - and hopefully you will score a bargain.
William Kelly http://www.happykoi.co.za