New L4

Great!

What do you have the intensity of the LEDs set at?

How many hours/day do you run the LEDs?

How often do you clean/harvest the algae off the screen, and how aggressively do you clean it? (hopefully not too aggressively)

Thanks for posting the results, @cbsaint01 got one of the first L4s

 

I would increase to 22 hours/day. Part of says go to 100% & 24/7 but creep up on that over the next couple weeks. Also let it grow a few extra days. You want to get to the point where it starts filling up the box like this:

 

Or this

 

Nice! I can't say I'm totally surprised, you had a solid base of growth to start with, so changing the hours in that scenario usually leads to a linearly predictable result (meaning 20% longer photoperiod will mean about 20% more nutrient uptake)

Water changes still have value beyond nutrient reduction, my instinct says to keep doing what you are doing so there are not any "wild cards" thrown into the mix...if that makes sense.

 

If the previous change you made gets you where you want, I would leave it there for a while (two to four harvests) before changing it again. Sometimes you can "overshoot" your "set point" if you make changes too fast. When you start getting to the low nutrients point, that's where you want to make small changes and then observe for a while.

 

Yes that should be fine

I would continue with your previous husbandry routine, but I don't know that the increase can be attributed to doing only 5g vs 10g. That would not have made much of a difference

Possibly, it depends on the density of the algae you are getting. This can change over time as the system gets "cleaned up" for lack of a better term. I would go back to your previous cleaning schedule. Again, changing only one thing at a time and letting that "prove itself" over time is the best way to adjust things. So if you 1) changed light photoperiod 2) changed intensity 3) modified your water changes and 4) extended the algae scrubber growth period, it's a little hard to say what caused a rise in nitrates following a dip.

It appears that increasing the duration and intensity worked, so I would go back to 10g/week and the previous growth period and keep doing that for several growth cycles (2 or 3, at least).

What could have happened is that you had dense algae, and the extended growth period meant that light wasn't penetrating to the lower layers very well and that resulted in somewhat of a "stall" of growth, and possibly the algae starting to die off a bit and release some excess sugars back into the water column. Typically when you let it grow "too long" what will happen is that the algae will very easily detach from the screen, almost with no effort, and the algae remaining behind (still attached) will be much less. This is a sort of 'feedback' that you have to mentally store so that you know "how long is too long". If this is what happened (it happens to me when I go 2-3 days longer than I should) then I take 2 steps: A) reduce the light intensity (by 2 notches of the clock) for 2 or 3 days, then go back up to the normal level I have it set at, then B) from the day where I bumped the intensity back up, that is where I start counting days until the next harvest. So if I normally harvest every 12 days, I would go on reduced intensity for 2-3 days and then harvest again on day 15 (but if you wanted to go on day 12, just for ease of maintaining a fixed schedule, that is perfectly fine)

In my pic above that shows the full growth chamber, you can get away with several extra days because the algae is self-suspending, which allows light to penetrate deeper into the growth. I start to get this on about day 5 and by about day 9, it's over halfway up the box side walls. If you're not getting that type of growth (the true 3D growth) then you are probably still in the "cleaning up" stage of the scrubber/tank, and this is where there are still changes occurring in the system and nutrients getting sucked out. So the growth is a bit more dense, and going longer on the growth period might not work. i.e. you can't force 3D growth.

3D growth seems to really start to kick in when the system stabilizes, and sometimes that can take several months (depends on the system). But when it does kick in, it's hard to not get consistent thick growth. I have one tank that has a screen that is 1/4 deteriorated but every 14 days it grows almost the exact same amount of algae, and has for several years.

My personal tank (scrubber in my previous pic) has produced like that consistently for years, even when I replaced the screen, and then the entire scrubber. Once you have "conditioned" your tank/system with an algae scrubber, the ramp-up for a new screen is different (faster). So that tells me that there are phases that the scrubber goes through that are reflective of the conditions of the overall system

This is why it is difficult to apply what worked for one person to what should work for another.

 

Sorry, busy weekend

API test kits are always hard to judge in the 15-40ppm range, it changes depending on the light, angle, proximity to the card...I'll take your word for it that it's holding it there!! In theory, the levels should hold, so doing a bit of a larger PWC can't hurt.

The type of growth you are getting appears to be some finer GHA (not the dark green, dense stuff) so what I would recommend (probably too late, looks like you harvested already) is to give the screen a good rub with your fingertips under running tap water and loosen up/rinse away any loose growth, leaving a majority of the algae behind. You might not even dislodge much at all, but the point of doing this is to rid the algae mat of any detritus or slime growth (which should detach easily). You can go as far as taking the small toothbrush and swiping it across the screen (along the path of water flow) and that will definitely rid the screen of any slime type growth - it will also take some GHA with it, but that's OK.

You can repeat this process several times during an extended growth cycle. By extended, I mean that if you do this on day 7-10, it's sort of like a half-cleaning, so you would let it grow another 7-10 days and by then I would expect that you would start seeing some 3D growth towards the bottom of the chamber. This is the goal and I think you're nearing that type of growth - and while you can't force it to happen, you can help it by making sure that that algae mat is free of unwanted growth, which lets the light penetrate a bit deeper so you can let it grow longer (longer growth period)

You shouldn't need to continue to do this on a regular basis, once your 3D growth starts to take off and nutrients come down, you should eventually be able to set it and forget it.