It’s raining here! Unfortunately it seems like we are either in a drought or flood, there hasn’t been any significant rain in a while and now it looks like a tropical depression has parked itself right over the state. Hurricane season is right around the corner. The good news for me, I finished the filter build and it has been tested prior to the beginning of this deluge.
Starting with this post I’ll be updating the format a little, I’m going to put a section at the bottom of each post with information and links to any items used within the article. I think this may be better than just having links throughout, if you want to help support this site please check out any Amazon links provided as I am on their referral program. I’ll link to other sites as well but I’m only affiliated with Amazon at this time.
On to the filter build, there’s a lot of plans on the internet for different types of filters but the basic idea is to capture and eventually remove large solids from the water flow. One of the most common is called a swirl filter, this is where the water is swirled to create a vortex to trap solids. My design started with this in mind but changed a little bit as that didn’t seem to trap enough, I wanted as close to 100% removal as possible with little maintenance.
The first step was to build a stand for the filter to sit on. While not very exciting of a build, it may help someone out so I’ll cover it here. I measured the height of the fish tank and filter tank to figure out the height of the stand so your requirements will probably be different, but basically the top of the filter is just below the top height of the tank (using gravity flow for the water). Next step, cut the legs and shelf supports using 2×4 lumber:
For aesthetics and strength, I routed the legs so the shelves would be recessed into them. This also helps keep everything square.
Nailed together shelf supports:
Attached plywood to shelves:
Screw shelves to legs:
At this point I tested the height and made sure it was level in the location it was going to be installed. The pavers aren’t perfectly level so I figured how to orient the stand to be level and not wobble on the ground. Turns out I had to cut all the legs down by about an inch. You can see I also cut a hole in the middle, this is for the filter drain.
The final step was to paint it so it has a fighting chance against the elements. I had plenty of leftover exterior green paint left so that became the color of choice.
For the filter I had a 15 gallon tank that had previously been used as part of the water system for the house, a lot of designs use 5 gallon buckets but that just seemed too small. This tank had an opening on the top already but it was too small to work with so I cut around a ridge to make a larger opening but also tried to leave as much material as possible for strength.
Here it is with the cut off part removed:
Next I cut a hole in the bottom for the drain. I went off center to avoid a plastic seam.
“MADE IN U.S.A” – awesome. Bulkhead installed. I’ll put a link to the one I used at the end of this post.
The drain is just a PVC quarter turn valve from Lowes:
The aquaponic system doesn’t have any leaks and I want to keep it that way. Before going any further, a leak test:
Next step is to cut holes for the inlet and outlet pipes. The inlet (from the fish tank) is slightly higher than the output (to the media beds) to allow for the gravity flow through the system.
Uniseals installed. These are the most common types of seals used in home built aquaponic systems and for good reason, they work. Even if you have to go through a curved surface like this filter or a bucket they handle it with no problem.
Don’t let anyone fool you, pushing the pipe through the Uniseal is not easy. I’ve found it helpful to bevel the pipe edge slightly and use some soap as the directions recommend. Once you get the pipes through they do a great job though and they are quick and easy to install.
Here’s what the pipes look like inside the filter. The water coming in is to the left, it is directed near the bottom at an angle to start a swirl, then exits out the top.
Here’s how it looks from the side:
This design did work but the lighter particles still remained suspended and were getting through. One thing that I tried was to reduce the suction of the output flow by adding a pipe with holes. The idea was that this would break up the flow into more but smaller drains.
This did help, but the lighter solids were still not settling into the tank, instead they would eventually find their way out. I tried adding some screening to this pipe but it would clog up in a few hours. I added some plastic fencing rolled up near the top of the filter to break up the circulation but that only helped slightly. The final solution? I filled the filter about 3/4 of the way with lava rock. Bingo! This works great.
I know the swirl has been stopped but the results speak for themselves. The picture above is what the rock looked like after about a week of running, the debris at the top is actually algae growing but the water exiting is crystal clear. I left the additional filters in the media beds so I could see how much was getting through and with this setup it is very little.
Now the very last problem to solve was that there was algae growing in the filter since I had left the top open. This was solved by cutting the bottom off of a large nursery pot of about the same diameter and holding it down with a bungy cored. Maybe in the future I’ll come up with something more elegant but for now this works.
The filter has been in place for about three weeks so far and the water seems to be a lot cleaner. I have flushed the filter out weekly but it could probably go for a month or more between cleanings. One reason I’ve had to clean it more often is that raccoons have discovered the automatic fish feeder and have dumped the entire contents into the fish tank twice so far so that is something that will have to addressed right away.
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Links to products mentioned in this post
Uniseal – best prices I have found are from The UNISEAL Warehouse