Algae Scrubber Basics

[Floyd R Turbo]

This is where making sure your slot is 1/8" wide is important. When you cut the slot, it relieves the pressure of the PVC pipe and allows the gap to close. So you can mark the slot and cut it, but then when you measure it afterwards, it will be narrower than you marked it. So you may need to trim the slot again to make it 1/8" wide all the way. Otherwise, it can pinch in the middle and restrict flow. So check that.

The top edge of the screen that is inserted into the pipe, as well as about 2 or 3 rows below that junction point, should be left smooth. If you roughed it all up, then the algae can grow more easily into that junction and you can get sideways spray.

Draping the slot pipe with saran wrap will help prevent streamers. you only really need to have the saran wrap drape about 1" down from the junction point. You can use a piece of black plastic garbage bag also and this will have the added benefit of blocking the light and preventing growth all together.

 

[Brummie]

Has the feeding guideline been slashed. Ie 1 cube = 3cc, to 1 cube = 1cc?

 

[Floyd R Turbo]

Yeah I noticed that as well in SMs latest patent that he claims a cube is now not the size of an Ocean Nutrition-size cube but rather 1cc. I believe that discussion was had on his site sometime in the last year as well and he affirmed the ON cube size.

It's all dependent on the food also IMO. Something with a lot of water content would have less effect than a DIY food like I feed that is chock full or stuff.

 

[Chris Abbott]

Any other good scrubber threads? Looking for tank pics not pics of PVC pics of Displays! First reef, first scrubber here is how mine is looking.

 

[ca1ore]

Yeah I noticed that as well in SMs latest patent that he claims a cube is now not the size of an Ocean Nutrition-size cube but rather 1cc. I believe that discussion was had on his site sometime in the last year as well and he affirmed the ON cube size.

It's all dependent on the food also IMO. Something with a lot of water content would have less effect than a DIY food like I feed that is chock full or stuff.

Plus it's all guesstimating though, isn't it. I oversized my scrubber (dual sided, 12x10 screen), I feed about 5-6 cubes per day, algae grows like crazy, and my nitrates are negligible. So maybe not oversized after all. So much better than my old dump bucket monstrosity though.

 

[SantaMonica]

Plenty of threads around, going back to 2008.

 

[Editour2]

Can anyone tell me the post # covering "algae growth types"?
thanks in advance

 

[SantaMonica]

Phosphate flow out of rocks

Many people, when they get their scrubber running for the first time, get worried when more (not less) algae starts to grow on their rocks. It seems really strange, especially when nitrate and phosphate have gone lower than before. What is happening is that phosphate is coming out of the rocks. Remember, phosphate is invisible, so you can only see the effects of it, and it always "flows" from higher concentrations to lower concentrations (just like heat does).

Example: If your room is warm, and you put a cold object on the floor, heat from the air in the room will "flow" into the object until the object and the air are the same temperature. Example 2: If you put a hot object on the floor, heat will "flow" out of the object and go into the air in the room, again, until the air and the object are the same temperature. Now suppose you open your windows (in the winter). The warm air in your room will go out the windows, and it will get colder in the room. The object on the floor is now warmer than the air, so heat will flow out of the object and into the air, and then out the window.

Think of phosphate as the heat, and your rocks as the object, and your windows as the scrubber. As the scrubber pulls phosphate out of the water, the phosphate level in the water drops. Now, since the phosphate level in the water is lower than the phosphate level in the rocks, phosphate flows from the rocks into the water, and then from the water into the scrubber. This continues until the phosphate levels in the rocks and water are level again. And remember, you can't see this invisible flow.

This flow causes an interesting thing happens. As the phosphate comes out of the rocks, it then becomes available to feed algae as soon as the phosphate reaches the surface of the rocks where there is light. So, since the surface of the rocks is rough and has light, it starts growing MORE algae there (not less) as the phosphate comes out of the rocks. This is a pretty amazing thing to see for the first time, because if you did not know what was happening you would probably think that the algae in the scrubber was leaking out and attaching to your rocks. Here are the signs of phosphate coming out of the rocks:

1. The rocks are older, and have slowly developed algae problems in the past year.

2. The scrubber is new, maybe only a few months old, and has recently started to grow well.

3. Nitrate and phosphate measurements in the water are low, usually the lowest they have been in a long time.

4. Green hair algae (not brown) on the rocks has increased in certain spots, usually on corners and protrusions at the top.

5. The glass has not needed cleaning as much.


Since skimmers, filter socks, etc don't remove any nitrate and phosphate, and waterchanges and macro's in a fuge don't remove much, most people have never seen the effects of large amounts of phosphate coming out of the rocks quickly. But sure enough, it does. How long does it continue? For 2 months to a year, depending on how much phosphate is in the rocks, how strong your scrubber is, and how many other phosphate-removing filters you have (GFO, carbon dosing, etc). But one day you will see patches of white rock that were covered in green hair the day before; this is a sure sign that the algae are losing their phosphate supply from the rocks and can no longer hold on. Now it's just a matter of days before the rocks are clear.

 

[Floyd R Turbo]

Even though I think you have vastly oversimplified the explanation of this process, with respect to the fact that all forms of phosphate cannot just "flow" out of your rocks, the net effect of what actually happens seem to fit the situation.

Since a reef tank is fed organic matter (any type of food) and these foods have phosphate inside the cells of whatever organisms are being fed into the tank, and this gets processed (digested) and released, there is little anyone can do to eliminate phosphate from being constantly added to the tank.

The typical reef environment is one with high levels of calcium and high pH, and at 8.4 pH the process of precipitation due to calcium binding phosphate does occur at the highest rates. This form of precipitated phosphate does not simply "flow to a lower phosphate level" as you proclaim. Some kind of secondary chemical process needs to occur with lowers the pH at below 7.0. I have yet to see a definitive explanation besides bacterial cleaving or possibly some algae exudate, or both.

But you appear to be trying to claim that all forms of phosphate simply get released when phosphate is lowered, and that that is the only thing happening here. I can pretty confidently say that it is indeed not the primary cause. It is only a precursor if anything.

If this lowering of Phosphate were the one and only explanation, then I would like to see all the threads on GFO where this becomes an issue under heavy use and frequent media replacement.

Nevertheless, the process does seem to be:

Add algae scrubber to existing system
Algae grows from rocks
Algae eventually stops growing from rocks

I have seen this happen repeatedly. I have also seen nothing at all happen.

Bottom line. Don't try to explain things like this in such definitive terms when many have repeatedly pointed out the same things I just did on other threads, some quite a bit more lengthy and technical.

 

[SantaMonica]

I think simple, definitive terms work great for explaining to a first time scrubber user what is going on.

 

[Brummie]

Doesn't make any sense to me. So, why does the algae not grow on the rocks when the phos in the water column is higher? The only explanation it seems would be that algae exudates (from scrubber) actually propagate unwanted algae at least until a tipping point is reached, whether that's nutrient related or predation. Whatever the relationship, oversimplified statements are only useful if broadly correct.

 

[gregrocks79]

That and why is their product so dang expensive for what it is???!!?!

 

[SantaMonica]

why does the algae not grow on the rocks when the phos in the water column is higher

Because there is no gradient.

 

[hobbzz]

I've read most of the thread but I'm looking at sizing an ats on a tank with a skimmer. Just like the sizing guidelines are just that, guidelines...is there a general rule of thumb to start with when sizing an ats that will be used in conjunction with a skimmer instead of replacing one? Maybe 80% of the normal size or so? Thanks.

 

[SantaMonica]

I don't think it matters too much.

 

[hobbzz]

So just go with the normal guidelines? Thanks!

 

[Floyd R Turbo]

I've read most of the thread but I'm looking at sizing an ats on a tank with a skimmer. Just like the sizing guidelines are just that, guidelines...is there a general rule of thumb to start with when sizing an ats that will be used in conjunction with a skimmer instead of replacing one? Maybe 80% of the normal size or so? Thanks.

To me that would depend on the skimmer. If all equipment were sized according to "feeding", then this would be easy! Unfortunately they're not, so we are left guessing.

It doesn't hurt to have a little more filtration, so if you sized your scrubber accordingly and ignore all other filtration, you will have that much better of an overall filtration system. But I would not oversize the scrubber, build it to the guidelines. That way if the skimmer is taking a good chunk of the load, your scrubber is not significantly oversized.

So what size is your tank, how much do you feed, and what is the skimmer? Any other filtration besides the skimmer?

 

[Brummie]

Because there is no gradient.

Of course there's a gradient. This is how photosynthesis works. The nutrients inside the algal cells are bound up into organics within the cell when photosynthesising, thus the inorganic nutrient levels are depleted, which draws in more inorganics. Are you suggesting that where the algae is attached to the rock, it acts like a root system, supplying inorganics to the rest of the algae, which in fact are independent cells, just in series?

 

[hobbzz]

To me that would depend on the skimmer. If all equipment were sized according to "feeding", then this would be easy! Unfortunately they're not, so we are left guessing.

It doesn't hurt to have a little more filtration, so if you sized your scrubber accordingly and ignore all other filtration, you will have that much better of an overall filtration system. But I would not oversize the scrubber, build it to the guidelines. That way if the skimmer is taking a good chunk of the load, your scrubber is not significantly oversized.

So what size is your tank, how much do you feed, and what is the skimmer? Any other filtration besides the skimmer?

Thanks Floyd. Tank is a 300g, skimmer is an ATB 10.5 deluxe, about 300lb of rock, carbon (gac) and gfo, and I dose vinegar as a carbon source. I'd like to ditch the gfo when the ats gets into full swing though, and I'm guessing I could do without the carbon dosing as well but not sure.

Tank is set up and running but no livestock at the moment, old livestock is still in the old tank and new ones are in qt. When all said and done I'm estimating I'll feed the equivalent of about 4-6 cubes a day for a few years until all the fish grow out. Will likely need to resize the scrubber down the road. And about a sheet of nori per day. Thanks.

 

[Floyd R Turbo]

The full sheet of Nori adds maybe 2-3 cubes/day 'equivalent' depending on the size of the sheet. The skimmer is a good one, so that's taking a chunk out of things. I would size it for about 4 cubes/day and you should be in good shape for quite a while.

Since your tank has no livestock (at least not fish) then the scrubber will not really do much since it doesn't have much to do without urea in the system. So if you put the scrubber on right away, it might not get much for growth so you would want to be careful not to throw too much light at it. But I would get it on there soon so that it has a chance to get started before adding the livestock. Watch the phosphate level, if it's really bottomed out due to the GFO this can slow initial growth also. Once you start feeding this will then be in the water until it all can pass by the GFO so you will get better results.

Once the scrubber is mature, then you can start backing off on the GFO. The most common issue I have seen is that the nitrates drop out but phosphates do not. This is due to more natural mechanisms that remove nitrate than phosphate. Whether this happens or not is highly dependent on the overall system and maintenance. So would not cut out the GFO completely, but rather use it to "take the edge off" when needed.

Leave the carbon in place also.

The vinegar dosing might negatively affect the scrubber growth if you dose it in batches (same with vodka dosing). Biopellets do not seem to have this effect as they are more of a constant source. Neither does the Tropic Marin Bio-Activ product. Again these are only some people's results and may be system dependent (larger systems night not see this effect as noticeably) but it's worth mentioning for anticipating potential issues or at least noticing them as they happen and being aware of the potential cause.