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June 2005: Forum

trickle tower filtration

A form of biological filtration used for the rapid detoxification of nitrites and ammonia, the trickle tower utilises the power of gravity to shower the media inside of it that soon populate with good bacteria to aid in providing a healthier environment for your fish and other aquatic animals.

Used almost 200 years ago, the trickle tower was used for the treatment of human effluent, and now in the battle against phytoplanktonic algal blooms, the trickle tower has re-emerged in the use of fish ponds.

I am the owner of two such 'towers', one sized at 160 litres and the other at 300 litres. Pack with lava rock are primary bioligical housing media,  dacron (quilt wadding in some countries) for fine particle filtration, and square metre upon square metre of compressed bird netting for large particle filtration, my personal experience in the use of trickle towers was brought about by my previous use of in-pond submerged filters and small trickle towers, that combined with elevated fish loads lead to detrimental water quality.

Given the right design, and considerations in the building of a trickle tower, we all should be able to combat the dreaded algal bloom, and create a better environment for our aquatic friends.

MATERIALS NEEDED: For my project I used a 300 litre food grade tank, you may choose to use any container as you please, but beware those that once contained chemicals may be toxic to fish, and containers which have very thin side walls and have a tendency to flex when huge amounts of weight are bearing upon it from the inside.

You will need biomedia. I chose lava rocks, bought from garden and landscape stores. I used around 250 kilograms. Note that you'll have to prewash this media before use because of the red colouring. There are other biomedias you can use, but I have found lava rocks to be efficient in what I am using.

Bricks or your own homemade stands, that are used inside to create a open section at the bottom of the tank to create an area where the water will shower down. I used 100mm stormwater PVC pipes, cut around 15cms or so in length, with v-grooves through each one to allow water to flow through the pipes themselves.

A meshed area to uphold all the biomedia. I used some containers I had laying around as well as gutter trap used to block leaves in household gutters to hold the biomedia in. Note that you should choose a suitable type of mesh or crate and use anything to suitable to allow water through, but not enough to allow the biomedia to fall through as well.

Shower drain set and faucet. I prefer using large outlets, and have utilised 50mm outlet pipes. I currently flow 5000 litres through the tank. If you are flowing, say for example 10,000 litres, it would be wise to use to 50mm outlets. You could use smaller outlet holes, but I tend to find they can restrict the flow, and not allow the water to shower inside the bottom of tank, which I feel is essential to the tower working. I once used a very small outlet hole (too small to fit an adult thumb into, and this restricted flow severely, causing the trickle tower to be ineffective at combating algal bloom. Don't forget to pick up a threadseal tape if you're using a shower drain and faucet.

In the alternative to a shower drain set and faucet, you can utilise a bulkhead.

TOOLS NEEDED: Electric drill, and holesaw suited to the size of the thread of the shower drain. For my appplication, the thread of the shower drain was sized at 47mm, and I bought a holesaw at the exact size. You might also need to get your hands on a jigsaw to cut the mesh for the tank.

Now...to the pictures and what I did.

**Click on the picture to open a larger image

Tank connections I used these to create both an inlet and outlet from the tanks and barrels I have used to create filters. They consist of both a shower drain set and a faucet connector. The shower drain is pictured on the far right hand side, and was slid from the inside of the barrel outwards, leaving the flanged area inside the barrel and the threaded section outside of the barrel. There is an o-ring seal, pictured second from the left and this was used where the shower drain's threaded section was located on the outside. A plumber's thread seal is then used  on the thread of the shower drain to create seal. Next, the item located second from the right was used to tighten the shower drain to the barrel. It is akin to a nut that is used in conjuction with a bolt. This item is screwed onto the thread section of the shower drain that is located outside, and after you've placed the o-ring and the plumber's threadseal onto the shower drain. Last, I found it convenint to add in a faucet connector that fitted onto the remaining thread of the shower drain, after the bolt for the shower drain was fitted. A plumber's threadseal should also be used on the remaining portion of the shower drain thread prior to fitting this faucet fitting. The faucet fitting although not necessary for some installations allows extension PVC pipes to be fitted so you could have the tower a few feet or metres away from the pond, say behind a tree, bush or what pleases you.	Top to bottom : Faucet connector, o-ring, threaded section, shower drain.
A raised bottom The bottom of all my trickle towers have an open area at the bottom where all the water showers down. I feel this may add to the oxygenation of the water. For my towers I used 4 inch (100mm) PVC pipes to provide support to the mesh I used above it to support the biological media being lava rocks. The mesh should preferably be either grids that can be bought from koi stores, flourescent light covers (I think some people refer to them as eggcrates), the lid of the barrel you have, drilled with as many holes as possible providing they aren't so large as to allow the biological media to fall through, or gutter traps (which most Australians should find in stores like Bunnings for $2 per 10 metre roll, and can be tied together using plastic tie locks found in the electrical wiring section of the said store). Instead of the PVC stands and mesh, you could also use milk crates, and other crates that have open areas all around, just as long as you remember to raise the bottom area off enough to allow the water to shower down.	Above: Four 100 mm PVC pipes, cut at the same height as each other, and at a length slightly taller than the output, in my case it was around 15cms long. If you lookl closely, there are v-grooves cut into the bottom of the pipes so when water showers down into them, the water can escape. Above: Custom made grid that sits above the PVC pipes and are used to hold the biomedia above the open area at the bottom of the tank to allow the water to shower through.  Above: Additional meshing was used. In this case it was plastic gutter trap used to prevent leaves from entering the gutters of home. They are not large enough to allow the lava rocks to fall through, but large enough to allow the water to get through. I placed some of my large river stones inside to weight the gutter trao down. The gutter trap is not very wide, being around 10cms or so in width, so I used some plastic tie wrap found in the electrical section of some stores to tie up electrical cable to join this meshing together. Here's a picture of my trickle tower. It's so large it couldn't fit in the car. The barrel is food grade plastic, was made in Italy, came with a stand, its own water outlet tap, and a lid. It's around 1 metre plus tall, and around 1 metre in diameter.
Hiding the trickle tower  Given the tremondous size of the tower itself, some may find unattractive, yet its function belies its looks. In my application, I have created a waterfall and cascades area for the water from the trickle tower to output into. I used a range of concrete blocks, pavers and bricks, wtih soft underlayment before I placed the liner ontop. In addition to the trickle tower, the rocks, and the pebbles outside here provide additional areas of filtration and water turbulence to aid in the oxygenation of the water as it enters back into the pond. I would suggest cascades instead of a straight waterfall, as the higher amount of turbulence should re-oxygenate the water much more than a singular drop from a sheet waterfall.	You can see the trickle tower in the background. It sat atop a stand that came with the tank. Make sure you have a very stable ground and stand, as the overall weight of the tank should weigh past 250 kilos if you were building the same tank as mine with lava rock as biomedia. You can imagine how the paves created steps in which the water could cascade down.   The water had been in there for one week only and was horridly green, of course this being a new pond I expected the algae to bloom. There were no fish in the pond, except for two common goldfish. They are still there today. Above: Here we can see the rough waterfall/cascades taking place. First, I played around with the positioning of the rocks to create the effect I wanted, and then later I started to cover the area up with more pebbles and rocks. Bottom: As the days progressed the cascades were created.  Above: After some time this is what I roughly came up with.
What to expect after the trickle tower begins operations  Soon after the trickle tower beings operation, within the first week, expect large amounts of foam all over the water. If you can scoop this up with a net. This process of foaming will continue for some weeks and should settle down. In the following weeks, I noted the waterr going from green to brown and then to gin clear. During this time, the foam began to slowly dissappear. After a few weeks, or in my case, around 8 weeks or so, the water became clear right down to the bottom, which is around 3 foot down (90cms).	Typical of a operational trickle tower and very green water is the huge amounts of foam that is produced and may go on for weeks. Still waiting...the water was less green, and was brown in appearance. Be patient now, the appearance of the water is less brown and is starting to clear up. There is less foam then there was in the previous weeks. After which time, the pond will be less foamy and the water should be pristine. No more foam and no more green water....just some issues with birds...which explains the netting. When I first bought her, she was around 45cms long, and was the largest in my collection. There is still a small trace of foam, but the water is clear. Clean, clear water!!! At the point I had moved around ten of more koi into this pond. You can see netting at the front of the pond, as I was trying to capture the eggs during the spawning of one of my other koi. In the future, she and her mate will be spawning in another pond.
Cleaning considerations  If you have prefilter media like dacron (quilt wadding) it would be wise to only rinse and squeeze this media in a container containing pond water to release built up debris inside the media. In the beginning I had washed the dacron with a hose, only to find a mild algal bloom (very slight green tint) after each wash that would suggest the disruption of a large colony of good bacteria. As for the bird netting, washing direct with a hose to remove all accumalated debris resulted in little side effect to the water quality of the pond.