New Algae Scrubber newbie

You might actually have too much flow. 350 GPH on a 6" wide screen is about 2x more that you need. That can lead to adverse effects actually.

The whole 35 GPH/in rule, IMO, is out the window. I have started recommending that you begin with just enough flow to provide even coverage, or as close as you can get to it. You would only need to increase flow if you started running the LEDs at a very high intensity which (depending on your nutrient level in the tank) could lead to photosaturation. But for most, this is not the case - unless you are wanting to push a smaller scrubber into "overdrive" so to speak.

The "just enough" coverage usually equates to somewhere around 25 GPH/in of flow. So for your 2 screen system with 2x 6" screens, that's more like 300 GPH for both screens.

 

When was the last time you did a water change?

What brand test kit are you using?

 

Just using math, a 15% PWC would only lower nitrates from 40 ppm to 34ppm, and if you have a net increasing nitrate level, that's not much.

I'm not sure if you're experiencing any significantly negative effects of having nitrate at 40 or more or if you are more feeling uncomfortable with that level? Most would say 40 is too high, but the real answer is that it depends on what you're keeping and what kind of problems you're having. Certain corals have no problems in high nitrates, fish will be OK as long as the rise happens over time (they will be acclimated to it) so I'm just trying to check your "level of panic" so to speak

If panic is high or increasing as nitrates increase, time to do some larger and more frequent PWCs until you figure out what the problem is. 25% or more, one sometime in the next couple days, one within a week - really knock it down.

This might kick-start the scrubber into a better production point - i.e. with nitrates lower, it grows faster which adsorbs more nitrates, and it can drive it down. That's the idea

 

I understand what you're saying here, I am also of this opinion. This is a math issue - here's an example (not specific to your system)

Let's say that a system is 100 gallons and the filtration system is capable of removing 5ppm Nitrate from that volume per day. Now that's all fine until you factor in that an Algae Scrubber is a dynamic system, so the rate of nitrate uptake might be different at different concentrations of nitrate as well as other nutrients in the system.

Just for argument's sake, we'll ignore everything else except for nitrate uptake. Let's assume (I don't have any backing for this, so someone feel free to correct me if I'm totally wrong) that as nitrates rise, nitrate uptake decreases. So when nitrates are less than 10ppm, the algae scrubber (at optimum operation) takes up 5ppm/day from 100g volume. When nitrates are between 10 and 30, that drops to 4.5ppm. When nitrates are over 30, that drops to 4ppm. Just throwing those out there...logic would say to me that as nitrate concentrations increase, uptake should increase, but growth types also change as levels vary (from what I've seen) so I don't know if that necessarily holds true.

Now let's say that you add (effectively, through food that is digested/etc) 4.5 ppm Nitrate per day. That means the net export, when you're below 10ppm, is 0.5ppm/day. Between 10-30, you're at net zero. But over 30, you're at a net export of -0.5ppm, meaning, you're on a runaway curve of increasing nitrates.

I've seen that GHA grows bright, thick, full, etc at lower nitrate levels. This is actually one of the original "selling points" of the UAS, that it creates a low-nutrient environment within the growth chamber, because the water is recirculated many times inside the chamber and new (dirty) tank water is slowly circulated into it. The thought was that GHA grows the best in low-nutrient environments, because that's what appeared to be happening. Whether or not that was actually happening is up to debate, I've seen GHA grow explosively in very high nutrient water also, so IMO that was marketing with a stitch of anecdotal truth - it does seem that uptake ability (based on physical growth/volume) of a given device increases as nutrients drop. This is as long as you are feeding a decent food, so that there is a relatively constant flow of nutrients (even if you are testing zero).

That above is my basis for the suggestion to perform a couple large PWCs to knock the nutrients down. It might have the added effect of supplying some trace nutrients you could be missing, some of which might be acting as a limiting factor in algae growth. A "limiting factor" is something that, when the concentration drops below a given level, can result in inhibited algae growth (which might cause inhibition of nitrate uptake, as well as phosphate uptake)

The only other explanation I could think of with the information provided is that you have some old rocks leeching waste, but I don't think that's the case as you have had this tank with a scrubber up and running for over a year and had 0ppm at one point in time.

Maybe you had a crash of some kind, possibly a biological (bacterial) system crash? Maybe not enough to kill fish, LPS, softies, etc but enough to kill SPS (due to the nutrient spike).

If you weened off vinegar dosing slowly enough, and had good scrubber growth, you're not over-cleaning the screen, etc...that should not have been the issue. Algae harbors baceria as well so there should have been surface are to populate/expand

MarinePure relies on harboring bacteria, so that would take some time to start having an effect. Again, that's not (as far as I know) something that is going to be fast-acting.

 

Based on what you've written in this thread, the scrubber should absolutely be able to handle it all by itself. So there must be some aspect missing here. Pictures would help tremendously. Pics of setup, from a distance and up close, with scrubber lights on and off, with lights removed, pics of the lights themselves, pics of screen before and after harvest, pics of the volume of harvest, everything. I think some aspect is being significantly overlooked somehow

 

I can see a few issues. What's strange is that these didn't seem to be issues before (a year ago) but I may know why.

The lights are not very well positioned. I'm assuming these are the ones linked in the 1st post of this thread? They are a large array of low wattage LEDs. It appears that over 1/2 of each array is positioned above the effective growth area of the screen. In these pics, the light should be so bright that it affects your camera's ability to adjust, which is why I was asking for pics with lights on and lights off; however, in your pics, you can see everything pretty well. This tells me that those lights are not very effective, but I'll hold off on that conclusion until I see some growth pics.

The light that is in the middle pointing down is not going to be doing much. You really need intense light that is pointed directly at the screen.

The duct tape light blockers are fine, I don't think that you would get any effect from the parts of the arrays that are above the slot pipe even if you remove them.

I think the problem here is wholly related to the light fixture. I think you would get more growth (total) with one screen that is 1/2 the length (meaning, 1/4 of your total current screen area) and then light it up wit 2 of those PAR lights just like the one that you have in the center, except have them at worst positioned at the level of the slot pipe and pointing down at about a 30 degree angle. Ideally, you want those pointed perpendicularly at the screen (so at the centerpoint of the screen, pointing horizontally at the screen)

I think the 2 screen idea it what you needed to get things under control because of the lack of light intensity. That's a huge issue with your setup.

Now, regarding why it worked before - the answer is that it wasn't really working. What was likely happening is that your nutrients were sinking into the rock and sand over the last year, and now they are saturated and the nutrients don't have anywhere else to sink, so they are going into the water column. Meaning, your system was never at net export of nutrients, it just appeared that way.

 

I still think it's the lighting - that's not a lot of growth for ~18 days on that total area of screen. You should be able to get the same growth or better from a single screen that is half the size of one of your current screens using a more intense light. I don't think you're getting a lot of light to the inside of the 2 screens with the left light positioned as you describe, the PAR lamp is helping for sure (otherwise I don't think you would have 1/4 of the growth on the inside that you have).

What you have to look at is the total light that is hitting the screens directly, from the outside. Each array is only 45W of low-intensity light, and you're likely only utilizing about 50% of each fixture. So is your screen is 9.5" wide and the effective growth area is about 5" (that's what it looks like to me, roughly) that's 47.5 sq in on a single side, but you're only getting maybe 20-25W worth of light on that.

That's assuming that the fixture actually draws 45W - it probably doesn't. This is the marketing trick that fixture manufacturers use. If the 225 LED array uses 0.2W LEDs, each LED may not actually use 0.2W at full rated capacity (in the same fashion that a 3W LED only actually consumes 1.7W, but they still call it a 3W because that's what they used to actually pull) and they may not be running them at full rated current (because they last longer if you don't). Also, red LEDs that are labelled with the same wattage rating generally have a lower voltage drop at the same current when compared to blues or whites, meaning they operate at a lower wattage, so that makes it even worse.

Many manufacturers do this. They take the label-rating output wattage of the LED as actual (which it is not) and use that as the "actual consumed" power rating, then they do not take into account that they are operating it at a lower current than the full rating, and their fixture that they call "45 watt" is actually pulling more like 20W at the most, and could be pulling as little as 15W or even less. But for an algae scrubber, we care about actual wattage.

The manufacturers of the PAR lamps use the same trick, but the impact of it (on the scrubber builders) is a bit less because they typically use 1W, 2W or 3W chips instead of 0.2W ones. They still need to be "de-rated" but not to the extreme that the flat panel 200+ arrays need to be. That's why I said in my first or second post on this thread that this type of fixture has historically performed poorly - I've seen it work OK, but usually that's when it's used to the full capacity, meaning, shining straight on to a 10x10 screen, using the light as optimally as possible. Even in that type of case, one could build an equally effective scrubber using 1/4 of the screen and a more intense light.

The short answer to this is "yes" but the long answer is that you don't get the deep light penetration, so the active growth is really only at the surface, and everything underneath that top layer of growth gets quickly shaded as you go deeper into the growth mat, so it just doesn't grow at thick.

When I see a situation where someone uses a very large screen on a comparatively lightly fed system and then lights it as if they were feeding according to the screen size, that's where you get into issues with over-lighting and the growth being choked of nutrients, trying to spread out and use the whole screen but not being able to accept the intensity of light that is provided. That is a different issue than the larger screen / weak light scenario. The latter produces growth across the whole screen, but it will remain very thin - it works, but it (IMO) unnecessarily takes up a ton of space.