Submerged, rotating cylinder algae scrubber (with video)

So this is a new design I have been working on. I've been trying to come up a scrubber that can be installed in pretty much any tank, is very easy to clean, very quiet, and most importantly - performs well.

There is a 3d printed abs cylinder inside the acrylic housing, this is what the algae is (hopefully) going to grow on. A water pump pushes water past a small star type wheel at one end that turns the whole cylinder. The idea behind this is pretty simple - water inside the housing is forced out of the road by the rotating cylinder, so hopefully the boundary layer between the water and the cylinder (and eventually the algae) will be pretty small, allowing for nutrient transfer, which theoretically will mean good growth. The cylinder isn't perfectly round, there's little raised edges that run the whole length of the cylinder, which helps to force water out of the road as the cylinder rotates. The whole screen is illuminated from the opposite side of the tank (outside of the glass). This is a similar mounting style to the HOG scrubbers, where the screen is inside the tank, submerged, and the LED's are next to this on the external side. If it actually works, cleaning/maintenance will be simple. The white nylon rod gets pushed out one side, then you lift the lid and remove the cylinder to clean it.

I have made laser cutting files for the next version, which will be cut next week. Version 2 will have a few improvements, the main ones are:
The star type wheel will be made from acrylic (not 3d printed). Primarily this is to ensure no algae grows on the star wheel.
The lid to the enclosure will be held down by magnets. This ensures the lid stays on and that all water gets forced out the slit in the bottom of the scrubber.
Instead of the tubing pushing through a hole in the scrubber, it will push into a standard hose barb, which will screw into the acrylic base.
I've also got brackets to be laser cut which will allow the scrubber to be attached to the rim of the tank (if the magnets alone can't hold it in place).

Anyway, who knows it if it will work, or if it will be a complete flop, but it's been fun designing and building it. I bought this small tank on the weekend to test it the basic functionality out (only got round to it today). The main concern I have is that if the algae grows, it's a possibility that the algae may slow the screen down as it turns, possibly to the point where it stops turning. I'm not too worried about this though, the Eheim 600 pump I have it paired to has a pretty decent amount of head pressure, but it's something to keep in mind and monitor anyway. One other thing is that only about 25% of the screen is getting 100% of the intensity of the LED's at any one time. I really don't think this will be a problem though. The back and sides of the screen will still be getting a fair bit of light as it reflects around the enclosure and hits the screen. Upping the photo period will also help.

The video below is the first version - just to test basic functionality of the rotating cylinder so it's nothing fancy. I don't have the LED heatsinks yet, so I can't finish the LED housing side. I did connect up a couple of LED's just to show how the enclosure will be illuminated. Once I get version 2 made, I will move some fish and live rock into this tank, and feed one cube per day. That's what this scrubber is designed to handle based on the circumference and length of the screen. I'll also show the LED control board I've made once it's mounted in an enclosure.

Anyhoo, here's a short video of it in action (without the LED side)

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I haven't seen anything made like this before, then again, I haven't really looked. I've seen ones where they are 50/50 exposed to air and water, but they were generally powered by air pumps, where'as this is completely submerged.

I took that scrubber down recently. I'm redoing the lighting on that tank so have to make room. Growth was better when the screen was surging though, which makes sense. The screen itself had no issues, algae attached to it well. Yeah that's the main reason why I went with the 3d printed screen - it's much nicer than just wrapping a nylon sheet around a cylinder, and it should grow algae just as well. I didn't look into injection molding because it's rather expensive initially, and probably wouldn't grow algae as well.

Sorry I didn't explain that properly. The cog/wheel below is 3d printed, and is glued to the end of the 3d printed cylinder. Mounted horizontally, the water hits the fans protruding from one side of the cog. This forces the cog to rotate. Since the cog is glued to the 3d printed cylinder, when the cog rotates, the whole cylinder does. In this build the cog is 3d printed, though in version 2 it'll be made from acrylic.

 

True, though I was planning on changing the style a bit (not just having straight fins). The circle at the top can also go, so I'll probably just glue a few 8mm laser cut pieces together. Will have a look anyway and see if I see anything that suits.

 

Not quite that fancy! Just perpendicular edges (at the end of each cog protrusion) which may give it more torque.

 

Have version 2 now, working on version 3. Going to ditch the magnets I think (except for the lid).
The brackets work well and the magnets I was using weren't cheap, they aren't really needed with the brackets. Damn it's a mission trying to do a neat job joining acrylic!

 

So version 3 is still a couple of weeks away at least. But recently I moved a few fish from my wall tank into the 10g tank that the scrubber will go on.
I recently purchased a Hanna Checker - Phosphate, so figure I may as well start taking phosphate and nitrate readings before the scrubbers in there, to monitor if/how they come down with the scrubber installed. I won't be doing any water changes on the tank which has recently cycled.
I will keep editing this post to update the readings, hopefully once per week. Took my first readings today.

Week 1 - No scrubber. Nitrate: 20ppm, Phosphate 0.44

 

Small update just to show a close up of the 3d printed cylinder and also the wheel (r1) (which will drive the cylinder). I got it laser cut in 20mm acrylic, I was going to 3d print it, but I don't want algae to grow on it, and I don't want another thing to have to print. There is a bit of warping as each fin is only 2mm thick, but it's nothing major.

 

I can't edit the post so couldn't update them. @Turbo do you know why/if there's any way around it?
Here were the readings anyway:
Week 2 - No Scrubber, Nitrate: 20ppm, Phosphate 0.15.

 

Ok dang, can't think of a way around it. I guess I could keep updating my signature, but that'll appear everywhere. Adding new posts will get messy fast. I'll just wait till it's up and running then make new posts each week from there.

 

Here's some pics and vids of version 3. This is the version I'll be testing with. Unfortunately even though I had a fair bit of live rock in the tank I planned to use it on, I don't think it can handle 1 cube per day. I was already reading some ammonia, so don't want to risk it. I'll be getting a larger tank at the end of this week hopefully, probably a 30/40 gallon, but I took some videos of it running anyway, just to see it in action. The scrubber and LED compartment can move up and down, they attach the brackets with m6 nylon screws. The top of the brackets allow for the scrubber to go any tank regardless of glass thickness, and if there is a rim around the top. There are 4 deep red LED's, one royal blue and one violet. The blue and violet combined channel output is always 1/6th of the output of the red leds. There's a 1/2 inch hose barb that threads in on the bottom right hand corner. The top lid is held in place via magnets. The 3d printed cylinder spins at around 100 rpm with the lid off, that will probably increase a bit with the lid on.











Showing the scrubber in action with the lid off:


Showing the LED's on/off cycle.
In this video 1 second = 1 hour.
So turn on and off approx every 12 seconds, just to show the automatic control of the LED's.

 

Thanks, time will tell, I'm looking forward to see if it works as well.

 

Nah they are solderless LEDs from RapidLED.

 

In the process of setting up a new tank for this scrubber. I'm tight on room in the stand I have for it, so have had a small 5g sump made.
A downside to this design is that the nylon rod running through the middle has to come out through one of the ends. So even though the scrubber is about 18cm from left to right, the nylon rod requires at least another ~20cm for it to come out the side of the scrubber. So in effect I need at least 40cm / 15 inches of width wherever this is to be installed, unless the whole unit gets lifted up out of the tank, which is a bit of a pain.
If this does end up by working, I think I'm going to modify the design, basically rotate it 90 degrees. Should make a number of things much easier.

Hopefully the tank will be up and running by the weekend, so will post an update then. It will need to cycle, but I guess there's nothing stopping me from running the scrubber anyway, not sure if the fact that it is cycling will impact any growth.