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RafflesGold Forums > Discussion Area > Green Water, Filtration and Tank Setup
I have had this fishpond 6ft x 4ft x 4ft in our frontyard for nearly a year now and as you can imagine, with strong sun light, we get a lot of algae, luckily from what i understand this is good algae, so its not so bad. The pond uses that the "experts" call a natural filter system (water runs thru 3 chambers, one containing tons of mesh, the other has coral and finally the 3rd one has a pump that pushes the water back to a water feature). I intend to redo the pond by removing the "natural filter" because cleaning them is a very tedious job and waste of a LOT of water. I was searching the web to look at some external UV filter and walked in to the fishfarm at pasir ris and the guys tells me, that the recommendation i find on the web (mostly are european companies) is only suitable for European weather, where Algae doesnt grow as much (and probably fishes dont poop as much). So i should go for a filter that is 3 times the recomended capacity. How far is this true?

My pond hold upto 2400 lts water and a pump of 12000 LPH, i was hoping remove the natural filters and install this external filter with UV (a hozelock 4500 costs about 260 SGD) but i am not sure if that is sufficient? The shop recommends i go and buy a 800$ SGD filter (which is way to big to hide behind the plants

Any advice?

Thank you
I would hate to abandon a nice three-chamber filter so here's what I'd do....

Replace the mesh in the first chamber with kaldness K-1 media. Do not put any aeration in the first chamber. When not aerated it is called a "Static K" filter. It would be best if the water could enter from the bottom and exit at the top of the chamber and you will need screens on both the inlet and outlet. The floating kaldness will trap the particulate debris as the water moves upward. To clean the media you would shut off the water, stir the media with a paddle, and drain the chamber. All the gunk will flow out and you do not even have to get your hands wet. It's very quick and efficient.

In the second chamber, remove the coral and replace it with kaldness media. Put several air stones in the second chamber to keep the kaldness media moving. This is called a "moving bed" filter and it provides excellent nitrification (ammonia -> nitrite -> nitrate). This second chamber will seldom, if ever, have to be cleaned, but again you would just stir it and drain.

K-1 media is not cheap, but it would be less expensive than replacing the whole filter and you will end up with a filter that really works.

In the third chamber, put some of the coral in with the pump. Coral will maintain the alkalinity but you do not need very much of it. The coral is difficult to clean unless you suspend it in a basket so that any debris falls through to the bottom of the chamber.

Put the UV in the line between the pump and the water feature. It is convenient to have valved bypass to divert water around the UV when you do not need it. You may find that the green water disappears for long periods after the filters mature and the UV can be turned off much of the time to save the bulb.

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