Here is a description she posted in another thread of the creation of this filter
Hi Fish and Dave, it's wonderful to meet the two of you. Yes, there is a big difference in upflow and downflow bio-filters, depending on how they are made.
We used to have 14 ponds where we bred Koi and Orandas. Our Koi breeding stock were imported from Niigata Japan and our Orandas were brought in from China and Singapore.
Our ponds were always either green or had hair algae. In 1982, we had no idea that we had to filter our ponds until they started to spawn and that's when the trouble started. Thankfully we made water changes every week because the ponds were so heavily stocked with fry. The upflow filters we used had lava rock as a bio-media and in the beginning they worked just great. In time though, the water would again turn either green or the hair algae would continue to grow although with the hair algae the water was always crystal clear.
Because I was so new to filtration at that time I had no idea that you had to either backwash your bio-filters or in our case, just dump them because we didn't have bottom drains and it was the only way to clean the lava rock. When I first started to dump the filters, I noticed that the bottom one third of lava rock was covered in this slimmy sludge. I did some reading and called some friends in the States because here in Canada, no one had any idea on how to get rid of these algaes and what the heck was causing it.
I was then told and I believe it even now that the reason why the water continued to have trouble with algae was due to the excess nutrients/toxins in the water which were being removed by the algae.
You can just imagine how much water I used to clean these filters because I knew that the sludge had to be removed from the lava rock because any good bacteria that had been started on the lava rock was being starved of oxygen and food by the algae.
A friend of mine found a picture in a book or on the net of this downflow bio-filter and when we started to use that it was like a miracle. The 13,000 gallon pond that we had was always green and the only time we saw our Koi was when we would bring them inside for the winter.
So, Hubby and a good friend of ours started to build this 300 gallon bio-filter for the big pond because a good reason for the water being so green besides the fact that we didn't have the right bio-filter and we needed something larger for the big pond was the fact that we had 60 Koi in that pond ranging in size from about 6 inches to just over two feet and, at that time, the only food that could be purchased for our Koi was trout chow. You do the math.
LOL LOL
So, we build the new filter and Hubby did something very smart by using a swimming pool pump to draw water from the bottom of the pond through a 6 inch pipe that had a bunch of holes in it. This worked very well and then the water started to clear. I was almost in tears.
The other thing that I noticed about the downflow bio-filter that we use is the fact that the bio-media we use never gets dirty. There is fine particulate around the medium but when we backwashed the big pond with a 4 inch bottom drain, most of that particulate was removed.
The other thing is that the downfilter we use is not like a trickle filter, I found that they worked very well also but we found that we had to clean the lid at the top of the filter that was full of holes so often due to the build up of algae from the pond.
This filter collects debris from the bottom of the pond to the top of the filter where it is trapped in window screening, keeping the plastic scrubbies that we use clean of the sludge. There is a pipe on the inside of the filter, raised up from the bottom about 4 inches, which fills with water as the filter fills with water and then draws this water back up to the top of the filter and out to the pond.
I'm sorry that I've gone on so long but when I think of all the years we had such trouble with algae and once we started using this filter it made my work on the filters so much less than it was. It used to take me a good part of the day to clean all the lava rock with the upflow and with the downflow, I just open a bottom drain or lift the scrubbies (bio-media) up with window screening so that I can put the pump into the filter and drain it and then replace everything.
Hope this makes sense to you.
