Building a Moving Sand Filter

[duanes]

Are you disappointed with the rainbow lifeguard or fluid sand filters generally?

Fluid Sand Filters are poorly understood. It may take 6 months for the bacterial to colonies successfully and they don't do any mechanical filtration so they never need to be cleaned (ever). Slow flow that stirs is all that is needed. They are dull boring reliable and extremely effective. Just safe guard against back flow and top up worn media as needed.

I agree with this, they are really only built for bio filtration (they do nothing for water clarity), although by using aragonite mine also accomplished extra buffering capacity as a reactor, another boring (yet often overlooked) attribute with the right media.
And why I built my own extra tall so media would not overflow and escape to damage pumps.
and used a pro quality PVC check valve to prevent the kind of back siphon that can ruin pump and impellers impellers. I also hung a filter sock under its effluent just in case.
And kept mine in the dark, to avoid algae, and because benificial bacteria are theorized to do a better job away from light, mine was actually under a basement stairway, to help avoid extra light.

 

[Ulu]

And kept mine in the dark, to avoid algae, and because benificial bacteria are theorized to do a better job away from light, mine was actually under a basement stairway, to help avoid extra light.

Yes, having mine in the open light is a mistake.

I'll probably use 4" ABS or pvc pipe with a small window glued in, or use clear pipe and paint most of the exterior. This will be in the shade 24/7, but it is still outdoors and with lots of ambient light.

BUT, I'm trying to promote evaporation in the summer to cool things, so I'm going to look into some flat plate designs.

 

[fishdance]

Just leave the algae to grow, it will only assist filtration. This filter doesn't need to be maintained at all.

Or use PVC pipe, no viewing window required. Either a strong spotlight behind or putting your ear against it will both let you know it's working. However if water is coming out ... then it's working. What else do you need to know/see? Even if only 20% of the media was fluid then it's 100% biologically effective.

The strength of this filter is its simplicity. It does best when left alone. As mentioned previously, its not popular because it's so boring.

If you do need to see inside then an open top cone (inverted) is probably the best option.

 

[Ulu]

I knocked the sand out of the Cobalt powerhead and the sand filter is still running.
Since the sand has been aging for months I am loathe to abandon it.

But it seems to be running slower and slower, which is why I thought the sand needed rinsing.

I thought these things were supposed to incorporate an air stone or air pressure to make them churn properly.

The churning is only 1/10th of what it was new. Pump flow is fine. It seems to be only channeling through a small part of the plate.

I may have another go at cleaning the thing out.

 

[Ulu]

The sand filter has now been running over 100 days. I'm going to keep it, as so far doing much else has seemed unnecessary.

Right after my last post, I found a hose leak. I thought I had a compaction problem, but a leak was slowing things down. Once I repaired that and added some aragonite it seemed to function well.

Algae in the filter has not increased much.I have not attempted to move it or do anything to fight algae in the sand filter (or elsewhere.) I grow it purposely in the patio tank, to feed those fish, but to also help remove nitrates from the 125g indoor tank. It is the largest of the three-tank system, and gets the least light by 1/10, and has zero algae so far.

 

[Ulu]

Guys I think I have solved every objection to my fluidized bed sand filter. It had failed on me over a year ago.

I have built one that is easy to clean, has an easily adjustable flow rate, And cannot back siphon into the pump.

The key here is to put the entire system including the pump and plumbing under water. By doing this there is no back siphoning, if the power goes off, because there is no head pressure when the pump is off.

This eliminated the check valve, and my flow control valve bypasses to produce a low flow plus extra aeration in the sump.

I put that valve on the pressure side so that it can’t get sandy.

If any part of my homemade system blows out the water all stays inside the sump.

There are more photos showing this underwater in my thread “patio tanks rock”.

 

[fishdance]

A very simple effective DIY design is to use an inverted safety cone (sometimes called a witches hat?) as the container with a PVC downpipe. The cones come in a variety of sizes (volumes) so pick the volume that suits your needs.

The cone shape allows water velocity to drop off as the diameter increases so sand finds it very hard to escape. Let the overflow spill out the top or add a drainage hole to direct output. You can view the media churn through the side if backlit.

 

[Ulu]

I looked at a road cone, but it smelled so much of thermoplastic I just didn’t want it in my tank. I was going to form up a cone from Lexan, but the new plastic was very expensive, and this was not.

I used a $10 bulkhead fitting & 3 gaskets at $1.79 ea. plus $5 in fittings & pipe. $2 for glue, a used siphon hose, so under $20 with tax.

I had the pump, but figure $30 for the cheap pond pump. Total then is $50 plus the sand.

This seems to be working well so far, because of the height, but I plan to “fan” the down pipe. I like the pressurized design (as long as it doesn’t blow!) because it is easy to run the output hose to a sock.

 

[Ulu]

I further reduced the flow through the sand filter, by bypassing 80% of the flow into sump circulation duty. This provides surface agitation and circulation and I love it.

Today I cleaned up the plumbing and sunk it further, to the bottom of the Brute.


I spent some time building a plastic rack for the filter socks and I added one more so that I now have four (One is in the 30 gallon pump chamber ) and I can easily rotate them weekly. That is to say, every week I will replace one of the 4 socks with a clean sock.

I used the aragonite sand because I want the water to harden up some more for the cichlids. Our water is really quite soft here and every time I change it I notice a die-off in the snails. I certainly wouldn’t want to keep shrimp. I have tried it and they don’t like our water.