View Full Version : New scrubber design/idea, please critique
02-21-2011, 08:29 AM
Am new to the idea of algae scrubbing, been reading on the forums for a couple of days.
Planning to set up a 8g nano-reef, focus on elegant/minimalist look, reducing equipment surrounding/above/below tank. Algae scrubbing seems a good bet.
Anyway, my idea is as such:
1. Find an transparent acrylic tube, watertight-sealed at one end, that can fit a spiral/straight/power compact fluorescent bulb, fairly low wattage for me since I'm 8g, but adaptable for other design needs.
2. Sew/stich a scrubber mat into a tube which leaves 1.5-2 inches all around the acrylic tube, a few inches longer than the length of the fluorescent fitting. Have something that looks like a dog anti-scratch collar (basically a big plastic funnel) that sits snugly around the top of the tube and provide a holding reservoir for water input. The water will flow into the large hole in the middle of the scrubber mat tube! (If you don't want light leakage, wrap the scrubber tube in aluminium foil for added reflectiveness!
3. At the bottom there is a collection cup and return tube to the main tank.
Length of the entire setup is variable, but probably the length of available lighting! The advantages of this setup is removing the need for reflectors, and near 100% light efficiency (minus a bit of loss at the ends). And can scale with using standard 2, 3, 4 foot lights, particularly single-ended power compacts. Also takes up a smaller area/volume of space, allowing multiple scrubbers to run next to each other in parallel if necessary, otherwise reducing the footprint of the setup to make it more discreet.
What do you guys with way more experience than me think about this?
02-21-2011, 09:24 AM
Not sure I see how it would be circular.
02-21-2011, 05:34 PM
Made a quick drawing to illustrate my idea - bottom picture is top-down view.
Can add reflector (tube of aluminium foil) around scrubber tube if desired, didn't add it in to make picture more cluttered...
02-21-2011, 05:46 PM
And the idea scales for larger setups...
02-21-2011, 07:04 PM
Ok it's just a round design with the light in the middle. Is a one-sided scrubber. Would be ok, but not as effective as two-sided of same wattage. And would be very difficult to clean.
02-21-2011, 07:18 PM
It sounds very doable. As I understand your design, the mat would be rolled up and stuffed down inside the tube, and the tube holds it in place as it unfurls. Cleaning would be easy: take out the mat, unroll it, and clean. I would be interested is seeing this built, randomaeiou.
02-21-2011, 11:59 PM
A bit like those overpriced phyto reactors you can get
I suppose it might be useful as a space saving idea in certain set ups. For instance a 100 square inch (one sided) screen could be wrapped inside a circular container 6 inches across by 6 inches high.
Not sure how you'd get even flow across the screen though
02-22-2011, 03:37 AM
So I thought about it a bit more, and came up with a more concrete plan, shown below.
Not sure if I need 2, maybe 3 separate inlets using a 3- or 4- way junction to split the flow evenly across the top plate to ensure even flow across the rolled up mat, but shouldn't be difficult to drill the necessary holes or fit the plumbing in either.
Otherwise should be a rather simple design... (Remember, I was aiming to algae-scrub a 8g nano, although my design has about 40+ square inches of fully usable scrub mat area and 18w of light in a volume rather similar to a can of soft drink - note the proximity of light to the mat, which should be well over double the recommended capacity! Admittedly flow is somewhat pathetic at ~150gph using a Marineland Minijet 606, but couldn't find anything stronger using a similar volume - space is precious in a 8g tank!)
Whole setup requires -
3" diameter *clear* perspex tube, 6" length.
Enough aluminium foil to wrap around outside of perspex tube - MMMOOOAR LIGHT!
2x 3" diameter circular perspex plates, 1 for top, 1 for bottom. Top needs a central hole fitting the lamp holder cut into it, as well as 1-3 holes for inflow tubes from pump.
1x 3" diameter clear *curved* perspex plate, for the inflow spreader.
1x ~1" diameter perspex tube, 1" length, to go around the lamp holder and join the top plate to the inflow spreader plate
9.5x6" algae mat
Cheap 18w fluorescent bulb with cheap lamp holder/socket - no need to be fancy as all the electrics are *outside* with much reduced exposure to saltwater
and a pump - Marineland MiniJet 606 in my case.
How does that list sound? Most of it is perspex, and not particularly complex shapes at it, with the possible exception of the curved inflow spreader plate. Estimated cost of materials - less than $30... possibly much less if all the bits of perspex can be scavenged.
Just wanted to say - inherently, this design should not leak (much) light, and should not suffer (too) much evaporation, which are potential problems for bedroom nanos - can't sleep when it's too bright, and nano water quality is difficult enough as it is to keep stable without dealing with massive routine evaporation.
02-22-2011, 06:40 AM
Build it, see how you get on.
But how about building one from two concentric acrylic cylinders?
That, if the flow could be controlled, would create a chamber of running water over the screen which might allow for "3D scrubbing" as seen in the chamber of the SM100 by some users (but in a much smaller device)
The bulb would sit inside the inner cylinder, as per your idea.
The power of the single bulb might be a limiting factor though.
02-24-2011, 02:08 PM
How about if the water entering a circular chamber could be made to swirl round it, perhaps by having a 90 degree bend in the inlet?
That might create a fair bit of flow over the screen if it was at sufficient velocity.
I might have a go at one of these myself
02-24-2011, 11:52 PM
So this is another updated design, drawn to scale. Have incorporated inner tube and done some rough calculations.
Unfortunately, commonly available lights comes at maximum 18w - if there are any better alternatives within size constraints I'd love to know. Trying to fit 16mm elbow in with the fluorescent bulb made me realize just how teeny this design is - it's gone from the size of a beer/soft drink can to the size of a can of tinned fruit! Had to increase diameter to 10cm to accomodate everything. Current screen width is ~12inches. Fully usable area is about 40-50 square inches, give or take. Based on rule-of-thumb numbers posted here on the FAQ and elsewhere, this should be enough for moderate filtration of a ~18-20g setup?
Calculation using 250gph gives 17+ m/s flow velocity within the 5mm gap, not accounting for the cross section taken up by the screen and algae, which will only make it faster. Using density of 1.025 and 15m/s flow and 5mm gap and the viscosity of plain water gives a Reynold's number in the region of 86000, which should be well into transition zone of turbulent flow, and could be into totally turbulent flow altogether. To boost this further, using a higher gph (I plan to buy an AquaClear 70 rated at 300gph/1185lph to run this setup, along with an inline heater and a Hydor Flo rotating outflow device, both of which *will* cause some flow velocity loss) pump and/or increasing the gap between the inner and outer tubes will work. An increase of the gap from 5 to 6mm leads to a 20% increase in the Reynold's number!!! (Well, not exactly, since flow velocity will drop, but hey... )
Am very excited by all this. Will need to find a plastics handyman to build this for me - I have little plastics DIY experience, but I know plenty of people that do! Have read, however, that acrylic soaks and warps in water and is strongly not recommended for applications involving extended water exposure, perhaps I might look at PVC or some other plastic instead! It seems polycarbonate is readily available in clear tubing form... I need 3 short sections of clear tubing of varying diameters, along with 3 circular sheets of 12cm diameter, 2 black/opaque and 1 transparent, shouldn't be too difficult, I hope... Oh, and a 16mm 90 degree elbow and a straight 16mm outflow, and plenty of sealant/glue.
(apologies about mixing imperial and metric - I work in metric, but it seems a lot of aquarium stuff is done in imperial, so I interconvert as necessary!)
02-25-2011, 02:50 AM
Not sure that a 5mm wide gap between the cylinders is going to allow quite enough space for the screen and any significant amount of algae growth. I think I'd try at least 15 mm there.
02-25-2011, 05:32 PM
Hmm, yes, I was worried someone might say that.
Simple solution would be to change the inner setup around the bulb - rather than use a thicker tube to leave 5mm of water space, it could be changed to just the tube around the bulb, and a simple plate at the top for spreading the water evenly. That one should leave a 5mm gap only so that the water is faster and less likely to allow algae buildup and clogging near the outlet. Haven't done my calculations for this, but I imagine the Reynold's number might suffer a hit somewhat...
03-22-2011, 10:44 PM
I was working up a design like this. I am glad I found someone else who is doing the same. Has anyone built this design yet? My only worry is that the light might get to hot and possibly melt the plastic. Any thoughts? One of the designs looks like the bulb is entirely sealed off. Also, I want to confirm that I am visualizing this correctly. There is an outer tube and then an inner tube that is barely smaller. A screen is inserted between them. The light is contained and kept from moisture within the inner tube. Does this sound right?
03-23-2011, 09:26 AM
There are one or two designs like this, which are effectivly single-sided (not as efficient), and I'll be posting them soon in the "OK" examples.
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