Koi Rescue
Phoenix Arizona

Cleaning My Biofilter - Backflush With Shopvac

One lesson I continually learn is that things that are easy to do, get done more often than things that are a pain to do. Cleaning my biofilter was one of those things I want to make super easy !

I did a lot of searching on bio filters, and not many people talk about how they clean them. Many of the biofilters filters seem to have a valve on the bottom which is opened periodically to drain out the mucky water. Then occasionally the owners seem to remove all the rocks from the filter, and adgitate them in a bucket with pond water, to clean the muck from between the rocks. If this isn't done on a regular enough basis, then an effect called channeling occurs, where muck gets trapped between the rocks and blocks off the water flow to only a few corridors in the rocks, greatly reducing the surface area which the water flows over, defeating the main purpose of the biofilter.

Then I stumbled on a few websites which showed using a spa blower from a hot tub, to pump air bubbles into the bottom of the filter. One site even showed the bubbling water, and wow did it look like it worked great! I got the idea of using my shop vac and built my bio filter with that in mind.

This is how I clean my biofilter. First I put down my bucket to catch the water, block off one of my return pipes, and attach a long piece of PVC to the other return pipe so it diverts the water to the bucket.

Next I hookup my shop vac, and attach it to the air blower in the bottom of the filter. I leave the circulation pump running the whole time. Look at how bubbly that water gets !!! If that doesn't shake loose the muck, I don't know what will !!!

There is also a lot of debate on the net of what type of rocks to use. Some like lava rocks because it is very bumpy, and porous. The little nooks and crannies in the rocks are supposed to provide extra surface area for each rock. The other side of the debate says that the lava rocks get all clogged up, so they don't provide as much area. Some thing pea gravel is the best, while others say it clogs up too easily because the space between the rock is so small, and the channeling happens rather quickly with them. Others say 1" river rock is the best, because it is round and the channeling won't happen so quickly.

I am sticking with lava rocks for now because they are very light, and the bubbling action easily shakes them loose.

After the bucket is full, I go water the plants in my front yard with it.