How do I get even screen flow?

[yesman]

Hi Santa, finally today for the first time I flipped the switch on an acrylic box srubber. I'm using a 30in x 10in double screen (cactus rough) that you made for me (it was your first screen to order I think?). The issue I have is that because it's a bit wavy due to stretching from the holesaw, the water flows down the gaps and not down the ridges in the wave as it exits the pipe. I followed your stats for size of cut in the pipe and it would work a treat if not for the wavy nature of the screen.
Any ideas for getting an even flow across the screen?
I have an OR 6500 for flow through 1" pipework and 3ft of head.

Thanks, Dan.

[sklywag]

Take the screen out and reshape it. Be careful not to kink it. I go through this after cleaning my screen. Sometimes you/I have to sort of roll the screen opposite of the bends in it.

[SantaMonica]

A pic would help. If it's when the water comes out of the pipe, then this will even out as growth occurs.

[Bridgeport]

Hi Santa, finally today for the first time I flipped the switch on an acrylic box srubber. I'm using a 30in x 10in double screen (cactus rough) that you made for me (it was your first screen to order I think?). The issue I have is that because it's a bit wavy due to stretching from the holesaw, the water flows down the gaps and not down the ridges in the wave as it exits the pipe. I followed your stats for size of cut in the pipe and it would work a treat if not for the wavy nature of the screen.
Any ideas for getting an even flow across the screen?
I have an OR 6500 for flow through 1" pipework and 3ft of head.

Thanks, Dan.
I had the same problem with mine.I widened the width of the crosscuts and it helped quit a bit. With me, I had to experiment a little to get it to flow evenly. Also widened the gap just a little to fit the double screen.

[yesman]

Bridgport-The cross cuts sound like a good idea to even out flow on the ridge section-thanks.
Santa-Will post photos, growth may even things out over time, for now the no flow gaps are wide, imagine a ~ where the flow only comes out of the troughs as the screen makes it wavy way along the pipe.
Skylag-the screen being double and cactus rough with stretching from the holesaw will not even out much at all.

[SantaMonica]

I see what you mean now. It's because the slot is wide, allowing the screen room to move from side to side. Try starting with just a 1/4" slot, which will keep the screen in place. A double layer screen can be a tighter fit, because it has room between the layers for extra water to flow.

[yesman]

Ok got some photo's to show the situation with the screen. The arrows indicate the troughs the water flows down leaving the ridges dry. The slot is an even line although it would appear wavy (it's the screen). The slot width is about 3/16s and quite tight.

[attachment=2:1b3n7aqd]Scrubber screen.jpg[/attachment:1b3n7aqd]

[attachment=1:1b3n7aqd]scrubber screen a.jpg[/attachment:1b3n7aqd]

[attachment=0:1b3n7aqd]scrubber screen 2.jpg[/attachment:1b3n7aqd]

[SantaMonica]

I wouldn't worry. You could make a smaller slot if you wanted, but as long as there is flow, it will fill in by itself, because there will be growth only in flow areas, which will slow the flow there and cause growth in the remaining areas. And being 2-layer, water is still flowing in-between the layers, that you can't see. Try it the way it is, and consider making another pipe in a few months if you don't like it.

If you make another pipe, you'll probably need to cut the screen vertically, so you only have to handle 1/2 at a time. With a tight slot, that full sheet is going to be hard to get into a tight slot; but 1/2 of it will be easy.

[yesman]

Thanks for the feedback. I will just let it run for a month and see what transpires and post up new photos.

[sklywag]

Now that there are pictures. It may also be your screen it a tad longer than your slot creating the rippled effect. In the second picture you can see the screen is sort of pushed into the corner instead of just at the end of the slot. Trim the screen a little where it enters the slot so it's not pushed together.

[mikepao13]

Had the same problem.

In my case the screen was too long and due to light and head it was not straight down .

So i cut the sceen to 3 pieces with just half cm gap between them.

Now the flow is great and even on every part of the screen.

[Gigaah]

I've been messing around with other slot configurations and methods to flow over a vertical screen because I think this is perhaps one of the faults that probably hangs a lot of people up. Currently I have a pipe with two 1/6" slots (like if you ripped the pipe down the center). The water flows out these two slots wich are situated 90 degrees off from where the normal 1 slot is. the screen is hanging from shower curtain rings but is touching the pipe. The water flows out each slot one slot feeds one side of the screen and the other slot feeds the other side of the screen. It works pretty well really. Except for the fact since the water flows over the pipe it takes about 2" before it reaches the screen so that is one..semi issues I'm trying to work around.

[Bridgeport]

I've been messing around with other slot configurations and methods to flow over a vertical screen because I think this is perhaps one of the faults that probably hangs a lot of people up. Currently I have a pipe with two 1/6" slots (like if you ripped the pipe down the center). The water flows out these two slots wich are situated 90 degrees off from where the normal 1 slot is. the screen is hanging from shower curtain rings but is touching the pipe. The water flows out each slot one slot feeds one side of the screen and the other slot feeds the other side of the screen. It works pretty well really. Except for the fact since the water flows over the pipe it takes about 2" before it reaches the screen so that is one..semi issues I'm trying to work around.
Can You show us a Pic ?

[Gigaah]

In another thread here it has been suggested and tried by another user to drill 3/16 holes every 1/2" to even out the flow. That poster identified correctly the problem that is present is the velocity of the water. It doesn't like to exit the pipe early into the slot because of it. The flow is heavier at the end of the pipe I'm seeing because the water slams against the end of it and THAT is where the back pressure builds first from what I'm seeing. I Have a relief hole in the end cap of my pipe. Its like 1/4" ID tube. I'd rather have it for saftey incase the pipe clogs up too much and prevents the overflow from flowing enough to keep up with the return pump.
Given that my slot configuration seems to work well except for the first 2 inches. I am going to drill some holes in it when I clean the screen in a day or so. I'll report back on the results.

picture of my current slot configuration
[attachment=0:2i6m3at5]IMG_3175.JPG[/attachment:2i6m3at5]

[SantaMonica]

Once growth goes up into the slot, however, it all will even out (provided you do not have a light-shield).

[Gigaah]

I've actually had problems with the algae growing up into the slot. It clogs it up and creates high pressure and starts to spray out and tottally screwed up my flow for the rest of the screen. I was getting lots of brown.

[yesman]

Gigaah-is that with 7-day cleanings?
Skylag-the screen does end right at the cut, it came wavy/stretched from the hole saw action.

For now I've set the system up and will let it run. In a couple of the gaps water is trickling down between the screens and with time things may even out a little. I'll now wait and see how well the algae covers the screen and how it affects flow from here and then see what to do next. No light shield at this stage.

[SantaMonica]

Just remember that a double screen can have a really tight fit, because the flow goes between it.

[yesman]

Here's the screen after running 48hrs. Notice the streaks between growth and the ridges that arn't receiving water although some water flows between the screens in places causing algae growth. The screen is 30" long x 10" wide and lit by twin D-D razorlights either side with 3000k tubes 18hrs on 6hrs off. This is a remote acrylic box plumbed through the wall to the room behind the tank, fed by an OR 6500 and gravity drain return back to the sump. Makes for a shelf based easy access, easy clean scrubber system.

[attachment=1:pprt3ong]scrubber @ 2 days.jpg[/attachment:pprt3ong]

[SantaMonica]

I think it will be ok.

[yesman]

As you can see above at day 7 theres pretty good coverage although there are white streaks both sides with no growth. At day one the nitrates were 5 and at day seven they are 2.5, while phosphates were 0.03 on day one and and day seven reduced to zero on salifert tests.
The coverage at day seven looks quite thick but there isnt really anything to scrape off yet.
How long before the first scrape?

[SantaMonica]

Clean now. It could really handle more flow, but if it's working then you can leave it.

[yesman]

OK, first clean, both sides. I upped the water flow a little which is now almost level with the bottom of the screen, the drain wont handle more without the water level going above the screen base. Lots of water flowing down between the screens, this is almost like having four sides of screen.

[attachment=0:2getzmtr]Scrubber first clean.jpg[/attachment:2getzmtr]

[SantaMonica]

I had thought that you were maxed out in flow. If it is still adjustable, give it as much as you can; it's actually good to have a little pool at the bottom.

[yesman]

Yeah I've got more if I want it, just concerned over the 'pool' rising too high in the box. Kinda funny at the moment as most of the flow is now cascading down between the sheets. So are you saying it's ok to have some of the screen below water ie an inch in order to raise flow rate?

The pool at the bottom is now green on all sides and humming with pods. So far there's just a pair of Jawfish in the main display spending all day hovering over their holes plucking pods from the water collum.

I also wanted to ask you re CUC and algae eating fish such as tangs and blennies. If the scrubber dominates the algae concentrations does this mean less snails/tangs/blennies in the display as theres little green for them to eat without supplementation?

Thanks.

[SantaMonica]

Yes you want the screen in a pool at the bottom

Yes there will be less food for the tangs, unless you feed some it to them, or unless you start feeding liquid coral food which will put giant amounts of N and P into the water which will grow more algae in the tank (and will cause corals to grow much faster too.)

[yesman]

Going forward I clean the screen every 7 days, both sides or one side? and if it's one side, then when 7 days is up I do one side and wait 7 days to do the other side, so one side will wait 14 days before cleaning?

[SantaMonica]

Split the screen vertically, and clean one half every 7 days.

[yesman]

Ok srceen at 14 days, algae now starting cover 90% of the screen. Perameters Nitrates 0 Phosphates 0 (on Salifert tests).[attachment=1:1j17gwh2]scrubber @14 days.jpg[/attachment:1j17gwh2]

Screen at 14 days with half clean and tap water wash down.
[attachment=0:1j17gwh2]scrubber 14 day half clean.jpg[/attachment:1j17gwh2]

[yesman]

Just wondering about the covering in patches over the sand in the main display of presumably diatoms its dark red/brown/green in places and thick. Is this still to be expected?

[Gigaah]

it will take some time

[SantaMonica]

It will go away.

[yesman]

Latest weekly growth. I've been cleaning the whole screen each week as to leave one half will mean cleaning every 4/5 days not 7 and weekends are how I want to routine the cleanings.

It's starting to get thick although with uneven flow some areas get less water, will also need to create shading at top as water starts to spit out sideways when algae grows into the feed pipe.

Santa, theres a constant pool of water at the bottom that grows out with algae and I scrape as much out as possible but inevitably once the pump is switched on again bits of algae get pumped back into the display and fly about all over the place before eventually settling down, do you get this? (The box is fixed to rigid drain plumbing so cant be moved).
I run an open system ie no filtering eg socks, carbon, filter wool ect wondering maybe a tang would act as cleanup crew for the floating green bits.

[attachment=0:zgkheeif]scrubber screen 1.jpg[/attachment:zgkheeif]

[SantaMonica]

A tighter slot, or more flow, will even it out. You also could try slipping a 1 inch strip of screen into the slot, which will make it tighter.

You also could just cut the screen vertically, remove half, and tape up the slot with scotch tape. This will put all the flow and growth onto the remaining half. This is an easy way to test what happens with more flow in the slot you have now.

Since it's growing well now, you can do your half-cleanings every 7 days, which will give 14 days for growth. You can only do this when the growth is very strong, so that the strong new growth compensates for the increased pods. I'll post a vid of mine doing this.

I get one or two handfulls of growth off of the bottom. I pull it out, then use a toothbrush to get most of the rest. Then I use paper towells to get most of the remaining water/pieces/particles. It's mostly dry when I turn the water back on, but some particles do flow into the tank (and yes the tangs go crazy). But even without tangs etc, the little bit of particles will just go away (or feed the corals), because now they are competing the huge amounts of algae growing in the scrubber.

[yesman]

Starting to get strong growth every seven days.
[attachment=2:8eujgx6d]scrubber end.jpg[/attachment:8eujgx6d]
[attachment=1:8eujgx6d]scrubber view.jpg[/attachment:8eujgx6d]
[attachment=0:8eujgx6d]algae weight 7days.jpg[/attachment:8eujgx6d]
3lb 3oz in drained weight from 300sq in screen in 7 days.

[yesman]

Because of water flow issues once the algae is growing up into the slot, I clean it all off completely every 7 days. However as you can see with over 3lb in weight of algae every 7 days being scraped off the screen and with nitrates and phosphates at zero it may be ok to clean this way. Interesting to note that at the bottom of the acrylic box the water level is about 3in with algae growing all over the acrylic and alive with pods, even some amphipods!

These photos show the screen after cleaning, plenty left on the screen in the first photo to kick-start the next 7 days growth. In the second photo with the screen in silouette you can see the layer of algae trapped in between the double screens. So far i'm leaving this in there to act as kick start to next 7 days growth.
[attachment=1:2500rgy2]scrubber sde view 1.jpg[/attachment:2500rgy2]
[attachment=0:2500rgy2]scrubber side view.jpg[/attachment:2500rgy2]

Any ideas on implements to block light from the 1st 1in along directly under the pipe?

[SantaMonica]

Two plastic strips, laid over the pipe, or attached to the pipe, will do it:

http://www.radio-media.com/fish/UserToddoOnAS-3.jpg

http://www.radio-media.com/fish/UserJdlOnAS-2.jpg

[yesman]

Excellent thanks.

[yesman]

Another update and a couple of questions.

08/08/10
Getting more even coverage on the screen and as I add stock to the new system the algae growth levels each 7 days are rising dramatically, this week 6 1/2 lb... thats almost a pound a day!
[attachment=2:3uyowxjw]scrubber080810.jpg[/attachment:3uyowxjw]
[attachment=1:3uyowxjw]scrubber 080810.jpg[/attachment:3uyowxjw]
[attachment=0:3uyowxjw]scrubber end 080810.jpg[/attachment:3uyowxjw]

[yesman]

[attachment=0:y9admlf2]scrubber weight 080810.jpg[/attachment:y9admlf2]

In the shot last week I used a side plate, this one's a dinner plate! Amazing growth in 7 days.

Questions:
In the beginning I placed a large handful of racemosa caleupa/grape caleupa and some cheato into the refugium to kick start the pod population in the system. Now 9 weeks later it's spreading through the sump fast as if there was no competition from the scrubber. I have it lit 18 hours per day from one 39 watt 6k T-8. Why the strong growth here and not being out competed from the scrubber?
If the scrubber is the only inorganic export mechanism and no water changes are being implemented what is the longer term effect on the ionic balance of the system?

[SantaMonica]

Nice growth... must be a record here. The growth on the left half of the screen is perfect spaghetti-type algae.

Your other macros are still there because you are still just not scrubbing strong enough. A scrubber can only pull out nutrients based on how many photons of light it is receiving. Although your one bulb may seem bright, and it may seem to be growing a lot, it could grow much more. There are definately enough nutrients in the water do do it, otherwise the other macros would be gone.

Doubling the bulbs would give twice the number of light-photons per unit area, thus allowing it to pull twice the nutrients out per unit time. Of course, this would fill up the screen twice as fast. In your case, however, it seems like your screen is already physically maxed out in 7 days (is probably undersized), so the double-bulbs would loose their growth effect after the screen started getting thick (because of shading).

The important thing is if your tank is the way you want. But if you really want to out-compete the other macros (without adding screen size), you could double the bulbs and start doing 3D scrubbing, which artificially gives more "area" or "volume" for the algae to grow and contact the water. You do this by raising the level of water in the box to about 1/3 the height of the box. As the algae grows, the bulk of it will start backing up the water even more, and the water level will rise even higher. As the level approaches the top of the box, the algae will be fully filled-out from top to bottom and from screen to wall; you will then have the most filtering power that you can have with that size screen. Actually could try this without adding bulbs too.

It gets to be a delicate balance when you are trying to extract the most power possible out of a given size. The power maxes out when the box is full to the top with algae and water, but then you have to watch overflowing, and then, as soon as you clean it, the power drops.

As for long term ionic balance (except of course for cal, alk, mag and str), it ends up being the same as the ocean, since algae is what controls the balance in the ocean too. In other words, the more algae-based your filtering is, the more your system is like the natural ocean (which is all algae based). The algae remove ammonia/ammonium, nitrite, inorganic nitrate, inorganic phosphate, metals (like copper, aluminum and iron), and CO2 out of the water. Alkalinity may in some cases be decreased (depending on your system's aeration), because of algae's slight use of bicarbonate to get CO2 when there is not enough CO2 in the water. Lastly, organic molecules are put into the water: Carbohydrates, vitamins, proteins, enzymes, lipids, and these amino acids: valine, leucine, tyrosine, phenylalanine, methionine, aspartate, glutamate, serine, alanine, and proline, which are what corals need.

So in addition to your normal cal, mag and maybe strontium additions (which are not algae related), you'll want to check and keep the alk up, by adding baking soda. I add about a half cup of baking soda a week to mine. So based on how much aeration your system has, you'll want to add up to about 3 or 4 cups a week. Just go by the alk tests. Also, if your growth ever starts to yellow, you can just add a little iron to make it green again.

[yesman]

Thanks for the detailed reply. Very interesting re long term Ionic balance. Strontium I have not measured or looked into yet. What about Iodine, whats your thoughts on it?

Just to confirm, the T-8 single tube is over the refugium macros, on the scrubber I run 4 T-5 tubes on a D-D Razorlight, thats 4x39 watts 3000k tubes, two either side, hence the reason I'm getting such tremendous growth from 300 sq. in. of screen and zero Nitrates/Phosphates.

[SantaMonica]

Ah ok, but the extra bulbs concept can still apply.

Iodine is used by algae, but is supplied by nori, if you feed it. I have not done any testing for Iodine.

[mikepao13]

Hi mate,

very nice setup. What type of lighting set are you using?

[yesman]

Sorry for late reply. I use the twin Razor lights form D-D (Gieseman). One 30" twin T-5 light each side for 156 watts total to light a 300 square inch screen (10"x30"). Produces strong algae growth, cleaned every 7 days to keeps no3 and po4 at 0.

[mikepao13]

OMG

thats great!!!!!!!!!

you are using only 156 watts on a total 300 sq inch and you have that much grow?