New Algae Scrubber newbie

I would say that it can, but that's not always the case. A lot of that depends on the dynamics of your individual system, there are many factors that come into play

In most cases, getting Nitrate to zero is not difficult. Getting Phosphate to zero can be hit or miss. IMO with phosphate, what you really want to shoot for is stability, and also IMO the 0.01-0.04 "target" level is questionable.

I think a lot of the time people focus on N and P when they see algae growing in the tank, thinking that is the one and only answer - getting these down. While that is one of the factors, it's not necessarily the only one.

Also remember that your screen is only a few months old, and if I'm reading this thread correctly (from the beginning, scanned it quick) your tank is not that old either. Check out #15 here: Mything the Point, Part Three: Conclusion - Reefkeeping.com

 

Looks like your phosphates came down pretty well!

You might be starting to approach a point in your overall system where you are hitting the bottom end of the nutrients. When that happens, it can start to starve your scrubber and you might see what you are seeing....so now, you might have too much light & not enough nutrients.

A lighting tweak might be needed. If you can't dim, you might diffuse it and/or reduce the photoperiod.

The other option is the "feed more" method, which I don't prefer.

 

I'm not sure what you meant by this, I could take this to mean that you are thinking that the brown algae is lowering phosphates, or maybe you think that it's turning brown because of the lower phosphates?

What I mean with my comment on phosphates was just that the scrubber appears to have lowered the phosphates well - I didn't mean to imply a connect between the brown growth and phosphates.

What I was saying is that now that your nutrients are reduced in the system, the light level/intensity might be enough to start causing some regression in the growth that you were getting. So whereas the light was good, and the growth reduced the nutrients, now the light (which is the same as before) is now possibly a bit too much, and this is causing the growth to shift away from GHA and over to brown algae. I would generally consider that a regression in growth types.

 

Basically, you should be able to match the feeding input to the algae growth output and get GHA in just about any situation, as long as you are still adding food to the tank (and have live inhabitants, etc). Phosphates don't necessarily have anything to do with it, not directly.

The balance is between light, flow, and nutrients. If these are all balanced, you should get decent growth. If you have an excess of nutrients, but it's not extreme, you should still get good growth. If your nutrients fall, and your light and flow stay the same, sometimes you will still get good growth, but if growth changes, this is an indication of imbalance between the scrubber and the system.

So, you could increase flow to try to deliver more nutrients (meaning, the same concentration of nutrients, just faster) but this will just deplete them better. So, not that.

You could increase feeding, that would add more nutrients and thus raise the concentration, and you might get GHA again. But that's "feeding the scrubber"....

So the other option is to adjust the lights for the new conditions and find a new balance point. It's not that the water is N&P starved - it's still there...when hobby-grade test kits read zero, it's not really zero. It's just below the range of accuracy. I'm kind of splitting hairs here (starved is an OK term to use)...lol

 

That can also be a factor. I don't have any concrete evidence or a study behind this, but when it comes to carbon dosing, there seems to be 2 general types of strategies: media and liquid.

Media-based carbon dosing, I feel, is more "gradual". If you do it right, it's more of a drawn out process. This seems to work OK in conjunction with a scrubber.

Liquid-based carbon dosing (sugar, vodka, vinegar) tends to be more sudden, more of a "shock" to the system - even when it's added to ATO water. I'm not exactly sure why, but this seems to affect a scrubber negatively. It can result in browning of growth...at least, that's what I recall. Usually the story I hear is along the lines of "I can only get brown growth", so if you started getting GHA, P wasn't lowering, so you started vinegar and then you got brown, that could be connected.

Whatever you do, don't make drastic changes. Keep dosing, but maybe back off to about 75% of what you are dosing and see what happens. You might slightly adjust the lights too, but not drastic. Normally I say change only one thing and then sit back and observe, that's the only way you can be sure of the effect of what you changed.

I would back down the vinegar to 4.5 to 5ml/day, and leave the lighting where it's at for 1 or 2 weeks. Just see what happens. Your algae scrubber is not likely to completely die off, but I would be checking it every day.

After a week or two, if you haven't seen an improvement in growth (without a rise in nutrients) then back off the lighting

 

Sorry I've spent the last 3+ weeks mothballing my engineering company, moving, selling furniture, and trying to keep on top of any customer needs while becoming a one-man shop. It wasn't as smooth as I had hoped, I've pretty much been offline for a month. Filled five 20-yard dumpsters with trash, paper, and metal. Threw my back out in the process and had to keep going as I'm the only one actually employed at the company.

Meanwhile, I'm a month behind on building scrubbers on top of it all

I'll try to get back to you this week

 

generally I think you would just want pipe that is 2 or maybe 3 pipe sizes larger. So if you're using 3/4" pipe for your slot pipe, 1.25" pipe would be what you would need. essentially it would need to be large enough to slide over the end cap on your pipe, so I would grab one like what you use while at the hardware store and see which size pipe you can fit it through

Or if you use 3/4" pipe you could get my light blocker

Light Blockers

 

What has changed in the last year, anything?

Do you have a few current pics of your setup, and before harvest / after harvest growth pics?

 

So are you running 2 screens that are side-by-side as in end-to-end or are they like 2 pieces of bread, parallel to each other? I think the latter is what you are describing. If that's the case, effectively that's the same as lighting one screen from both sides and doing just one screen would be more effective in that regard. Single-sided screens have a disadvantage.

You really should not be having nitrate problems with a 6x9 screen and feeding 2 cubes/day on a 75 gallon tank, unless your "cube" is a larger cube, which might be the case. Something else seems like it's off here....