So here's the question.

[atoll]

Why is it so many people have no problem growing GHA in their tanks with all manner of nutrients, water quality, flow and just about any lighting conditions and yet......... They have problems growing it in a purpose made algae turf scrubber? :rolleyes:

[SantaMonica]

Time. The rocks have had month or years to accumulate growth.

[atoll]

Time. The rocks have had month or years to accumulate growth.
Well yes but that would suggest GHA would grow under lighting we would normally consider unsuitable for GHA growth. Often GHA arrives no sooner than the tank matures in some cases. In a scrubber light quality along with quantity and duration plays an important part in growing GHA. They don't seem to be as important in many people's tanks who's tanks can be overrun with GHA under just about any kind of reasonably bright lighting.

[Bacon]

This is the argument that GHA grows in tanks under the high K spectrum, so why shouldn't one use a high K spectrum in a scrubber? Meaning, it would make sense to run all cool white and royal blue LEDs or 6500K+ light in your scrubber since that's what it's getting in the tank, and it's growing fine. Sound logic on the surface, but you have to consider intensity.

In the tank, you have high intensity near the surface but lower intensity in the water. Also you have a spectrum loss with depth. The blues penetrate further, but the intensity is decreased. So you can get a lot of algae growth in the tank from the DT lights.

But in a scrubber, you focus down to the spectrum that grows algae the best. If you put on blues and there is no depth of water to cause the same decrease in the intensity, you end up with too much light. That's not to say that you can't make a scrubber work with CW and RBs...it's just a much narrower window of operation.

As you go lower and lower in the spectrum, you get much less intense light per watt and then you get into a range where you have a wider operation.

I think most people that have problems with getting a scrubber going are missing something. Usually trying to over-light thinking more is better, or making it too big (same reasoning).

[atoll]

I go back many years in this hobby. When I started out we only had T8s or was it 12s? Anyway there was little choice just growlux and nothlight tubes. PAR was unheard of and certainly had it been measure it would have been extremely low yet many still had no problem growing GHA in fact it was the only algae many could grow. Sure nuitrents would be very high but light levels very low in tanks covered in GHA.

[Bacon]

Right, I go back pretty far as well...30 years in FW to be exact. But you prove my point, you don't need much light to grow algae. What you need is the right light, and then you must provide an environment that is relatively better than than the DT for growing the algae.

What matters is the now. Now, we have much more intense lights to meet the needs of certain corals. This means that you have to 1) get the algae to grow and have a foundation of growth upon which to build, and then 2) give it the superior environment. I think many skip past step 1 and try to blast a new screen with too much light and it never starts properly. Also growth on rocks which have nutrients available is different from growth on a bare screen or substrate. The latter will take longer to gain a foothold.

[atoll]

Right, I go back pretty far as well...30 years in FW to be exact. But you prove my point, you don't need much light to grow algae. What you need is the right light, and then you must provide an environment that is relatively better than than the DT for growing the algae.

What matters is the now. Now, we have much more intense lights to meet the needs of certain corals. This means that you have to 1) get the algae to grow and have a foundation of growth upon which to build, and then 2) give it the superior environment. I think many skip past step 1 and try to blast a new screen with too much light and it never starts properly. Also growth on rocks which have nutrients available is different from growth on a bare screen or substrate. The latter will take longer to gain a foothold.

I'm not in disagreement with you just stating facts as I know them to be. Seems to me GHA will grow in almost all manner of light spectrum and intensity it's only the rate at which it will grow and or the type of algae that grows under various light spectrum which best suits it. I have seen GHA grow well under tubes mercury vapour and metal halides (HQI). We knew little of nutrients apart from nitrate but nothing of phosphate. Ammonia and nitrite was our concern in those days.

[SantaMonica]

You do need red, and strong light, and air/water interface flow, and attachment, if you want to grow algae *fast*.

Yes algae grows on rocks with white lights, but it's not growing fast. Remember that a scrubber (once growing well), can completely fill up in 5 days after a complete cleaning. The red simulates shallow water growth, which is where the greens mostly attach.

[atoll]

However to many its easier to grow GHA in their tank than in a scrubber that's my point. Seems the requirements to grow GHA in a scrubber are more demanding.

[Bacon]

You're missing one factor and that is once your screen is established it can out-compete tank algae, if maintained right. I usually hear complaints of people scrubbing algae out of their tank (physically) and then it being back where it was in 2 weeks. But the amount that they harvest is not significant (squeezed weight) compared to what a good scrubber can grow in the same period, once it's matured. The key here is --> once the screen is mature <--

[atoll]

Not missing any factors at all. Again my point is many people find it easier to grow GHA in thier tank than they do in a srubber for whatever reason. There can be many reasons why people with GHA in thier tank find it difficult in thier scrubber such as not enough light, poor spectrum, not enough flow and who knows what else all while they have thriving GHA in thier tank.

[Bacon]

Gotcha. there certainly can be other factors at play, such as chemical warfare. I've even read somewhere that certain corals and anemones can exude chemicals that inhibit algae. So in certain situations it might actually help to pre-filter the scrubber feed with something like carbon to counteract this.

[atoll]

I both prefilter and have carbon before my HOG2 scrubber. I am still getting a slime type algae growing in it. I have also recently put a DIY scrubber on my sump more as an experiment as I had some of the required euipment already. That also grew a dark slime like algae on both sides of the screen. I have 2 x 20w led units on an A5 scrubber each with 16 reds and 4 blues. I will take some pic's when I clean it again but it has only been running just over a week so I am not expecting GHA for a few weeks more but if it arrives sooner great. Am not unduly worried as any algae growth in the scrubbers has to be a goog thing, I juat hope they will grow GHA soon.

[SantaMonica]

One reason we use real rocks for the Green Grabber material is because algae already know how to dig into rocks. Algae do not know how to dig into plastic.

[atoll]

One reason we use real rocks for the Green Grabber material is because algae already know how to dig into rocks. Algae do not know how to dig into plastic.

Algae may not know how to dig into plastic but they sure do know how to attach themselves to plastic. I have seen enough internal power filters and the like with GHA growing on the smooth surfaces of the body. However smooth plastic of course it's not an ideal surface for GHA to attach too but it can attach to rough netting as in other scrubbers. It's just in some peoples scrubbers algae struggle to attach themselves it would seem.

[Bacon]

My guess is that any smooth surface that grows algae is actually growing algae on top of a calcification layer. Think about it. scrub your glass with a magfloat and any spots of coralline that don't come off, that's where the algae grows first and fastest. Scrape it all off with a razor and it takes a while to come back. Same with power head in your tank, they get a coating of coralline, and you can take them out and scrub but unless you soak in vinegar, that algae will come back fast.

[atoll]

My guess is that any smooth surface that grows algae is actually growing algae on top of a calcification layer. Think about it. scrub your glass with a magfloat and any spots of coralline that don't come off, that's where the algae grows first and fastest. Scrape it all off with a razor and it takes a while to come back. Same with power head in your tank, they get a coating of coralline, and you can take them out and scrub but unless you soak in vinegar, that algae will come back fast.

I could go along with the above apart from the fact often GHA appears well before any caroline algae appears on the glass. Often people can't grow caroline algae and often it only appears after a tank has matured for sometime and by that I mean 12 montsh plus. All tanks and water conditions are different with no two exactly the same even when people set two tanks up to be identical but still get different results. Anyway this has been an interesting discussion even though I am not sure we found the answer to the question Just like why no 2 tanks are ever the same even when set up identical.

[Bacon]

I guess I should have said that calcification in general seems to be the key, and that happens on all systems to some extent. So as soon as the surface you are using starts to get a calcification covering, then this actually is what the algae anchors to. Coraline algae just being one form of calcification

[SantaMonica]

Yes algae attaches to plastic screen, but that's because of the holes; the algae grow through the holes.

[Bacon]

I've let screens grow too long and everything comes out of the holes, on cleaning, leaving almost nothing behind except for some coloration and algae attached to various cross-pieces, and it bounces right back. I try to avoid letting it grow too long because of this.