New pond dilemma.

Dear sir,
I had hoped that the next time I contacted you , it would be to send you photographs of my new pond, for you to scan and show on you're web site. Unfortunately, everything has not all been plain sailing.
If I can give you a brief history of my pond building project without boring you too much. No doubt, you are well aware of the unbelievable amount of work involved in pond building, I have now found this out first hand.
The construction side started one Sunday afternoon,my wife, who may live to regret this, made the initial suggestion,that I should build a koi carp pond.whether it was made tongue in cheek by her or not I don't know,anyway I headed straight for the garage, came back with a garden spade,lump hammer, wooden pegs and several string lines.By this time Audrey my wife had set off in the car for B&Q, I can't remember what for, but from her point of view it was a big mistake.
By the time she returned what was remaining of our back lawn, was beginning to resemble a building site, crudely marked out,with the outline of a koicarp pond, as large as I could fit into our back garden.When I get an idea in my head I do tend to go at it with all guns blazing, and with all the turf removed, there was no going back, so I now proceeded to obtain every bit of information I could on koi carp pond construction.I suppose like most people from the outset, I was pretty shocked, not only at the cost but the incredible amount of work involved,in what by koi carp pond standards was going to be a pretty small pond.
Anyhow off I started, fortunately I am pretty practically minded and was able to do all the work myself.I had already had a pond for eight years, albeit small, some seven foot by six foot and only eighteen inches deep,probably more by good luck than judgement I had been quite successful in keeping goldfish, and ghost koi, who seemed to all thrive quite happily. As I obtained a little more knowledge I installed a small box biological filter, UV light,submersible pump.sludge was always a problem, so was green water ,but by introducing oxygenating plants and water lilies for shade , I managed to keep clarity etc within acceptable levels.
My water lilies thrived, but took a lot of years to get to the condition they are now at.This had a big bearing on the planning of my koi pond,I simply could not bear to get rid of them and have a koi pond with no plants,so I decided to keep the old pond, build the new one adjacent,and eventually join the two together.
What I ended up with was the new pond approx. nine feet six by eight feet six, by four feet six deep, constructed from four inch solid concrete blocks,seven to eight inch concrete base, four inch solvent welded bottom drain to filter system. The pond floor has about an eight inch slope to the central bottom drain. The construction included two coats of render, top coat reinforced with fibromix, which you advised me on thank you very much, followed by three coats of G4.
I based the filter system construction on the commercial filter bay type, mainly because of my very limited space , this included four two feet dia by two feet six deep circular plastic water tanks joined together by four inch solvent welded tank connectors inch and a half bottom outlets flushable to waste via gate valves on each tank . The first tank was to be the vortex chamber with water entering near the bottom to create the vortex motion, this also incorporates several brushes , the next two tanks contain japanese matting the fourth and final tank is full of brushes, from here the water is pumped back into the pond by a grunfos c/h heating circulator,through a 30 watt UV light, the water enters the pond through two inch and a half subsurface venturies.I have also incorporated a skimmer into the pond wall which will eventually feed a waterfall pumped by another grunfos pump. The system is mains fed through a water purifier which is fed into the vortex chamber.
From a construction point of view the biggest problem I encountered was from the comparatively low water table in my garden. Every single day I would spend what seemed like ages bailing out gallon after gallon of water. I thought, once I had laid the first course of blocks this would cease to be a problem, but of course unrendered concrete blocks as you know soak up water like blotting paper, anyhow I got there in the end.
Meantime I had transferred all the fish into a paddling pool situated on the patio, where they survived quite happily, I made partial water changes quite often.From here on things seemed to go downhill, the big day arrived when I was able to transfer the fish into the new pond, all thirteen of them. I kept a close watch on all the water parameters, everything seemed fine, no ammonia, nitrate or nitrite levels, pH was fine, then one day I had a visit from the dreaded heron who went with nine fish,
You can imagine how I felt, so with the pond being rather less populated than I had anticipated I decided to stock up with some koi,somewhat earlier than I had planned.I chose five koi, took my time over picking them, to me they all looked perfectly healthy, showed no signs of stress, were all swimming around quite happily, so I introduced them to my new pond ,for a few weeks, everything was fine, no apparent problems. Then gradually I noticed, one by one the koi seemed to become disorientated, bumping into the pond sides, and did not seem to have any alarm reaction, there was no visible signs of disease, and they would roll onto their sides.
One problem I had with the koi even when they appeared healthy was, they all had a tendency to swim up the bottom drain and into the vortex chamber. I stopped this by fitting a mesh over the inlet bend, I was able to stop them getting into the vortex chamber, but once they were trapped beside the mesh they did not seem able to find their way back down into the pond, I then regularly had to put them back into the pond myself. Have you come across this problem before, and if so is there a way around it?
Unfortunately now all my koi have died. In a last ditch attempt to try and save the remaining one I contacted my local vet for some advice,he sent the dead koi off to a veterinary investigation centre at Penrith where they conducted a post mortem. The findings were briefly as follows,a few minor haemorrhages present on the ventral surface of the body, and on the fin bases. No evidence of skin ulceration. PARASITOLOGY ........very low numbers of skin fluke demonstrated on wet smear, no evidence of parasites on gills.HISTOPATHOLOGY......examination of gill in progress. COMMENT...... despite our bacteriological results it is likely that we are dealing with a bacterial infection. Examination of dead fish for pathogenic bacteria is notoriously difficult. the presence of haemorrhages on the body surface would support a diagnosis of bacterial septicaemia. The problem I am now faced with is, which I would be very grateful if you could advise me on is, I am now left with two goldfish in the pond who up until now have shown no signs of any disease, and seem perfectly healthy.As a course of treatment the vet had suggested that that I mix a prescribed antibiotic in with the fish food, but of course at this time of year the fish aren't feeding.Ideally I would like to rid my pond of any remaining disease, by some type of treatment, which I hope you could advise me on, so that come spring I could gradually start restocking with koi,if it is possible I would like to keep the two remaining goldfish in the pond but not at the risk of passing on any infection.I am sorry if my letter has been rather long winded,but I would imagine you have felt the same kind of frustrations in the past that I am now encountering If any of my problems that I have encountered during my introduction to koi keeping are of any use to you to print on you're web site, or if anything can be learnt from my experience, or lack of it , please feel free to pass it on to any interested parties,if you do I would love to know.
Stephen, Cumbria. (Some of these questions have been added to the Questions & Answers page. Eric).