May 032021

The boxes have evolved again. I extended one to 600mm high so I can move the light further away to test levels a bit. Also got some coroplast and lined them with aluminum foil for the side panels but still using pizza box cardboard for the top.

I also got a peristaltic pump to test moving fluid around because I think the main problem I’m having is the water is too stagnant. At some point I read that duckweed likes stagnant water, but I think ‘stagnant’ in nature is still a lot more dynamic than a gallon of water in a pan in a box my kitchen. So I’m trying to figure out how to move nutrients around and keep the surface from filming up without disturbing the wolffia too much.

I’ve got a really rudimentary filter system with an acrylic pipe hanging from the basin in the water so I can drop in a tube to pump water from the bottom without sucking anything up from the surface layer. If I stir the water up a little it slowly pulls any algae to the tube and I can pull it up. That seems to be helping keep the algae growth a little bit in check but I need to make a less manual system.

The ‘sugar press mud’ trials have been interesting if not productive. I don’t think it provides enough nutrition for wolffia alone with or without light. But mixed with a little regular dirt it seems to increase growth above just regular dirt. Unfortunately the growth it increases is more than just the wolffia. It turns things into an algae soup faster than regular dirt and kills off the wolffia.

That seems to be the big trick here- limiting algae growth to give the wolffia a chance because everything I do do far that helps the wolffia helps algae a lot more.

I also tried a different species of duckweed called ‘Lemna Minor’ just because. It’s not ‘mixotrophic’ and doesn’t really fit my whole ‘space grits’ concept but I’m still just throwing stuff at the wall to see what sticks. I don’t think I like Lemna Minor much so I think I’ll try to find another wolffia variant to play with rather than a whole other species.

I think the next phase of this will be all about not growing algae, which if funny to me considering I wanted to grow algae before wolffia, but this experience is reinforcing the apprehension that kept from actually doing it. Algae is insane. I’m starting to wonder if I should get some little aquarium shrimp because apparently they help with that. I’d rather not because I’ll probably kill them and I want to learn to grow wolffia without critter assistance, but the more I read the more I think that’s probably the way to go at least until I get a better grip on what I’m doing.

Also I’ve moved away from my earlier obsession with time-lapses and microscopy. If I need to keep the water moving to grow them I’ll never get useful time-lapses so I need to rethink my ideas about using computer vision to characterize growth. I’d like to say I could try to ‘train’ a neural network to visually extract growth information from video, but if I was ever smart enough to figure that out I’m way too lazy now.

I have to give a nod to MakersLED t-slot LED heatsink housings. It just comes with the sink parts and fan, you supply the LED, power, and wiring. Really decent little kit here and works great with the 80/20 frame. I put a little thermal paste on, screwed down a COB LED, wired in an AC-DC converter for the fan and voila- a nice, modular little LED lamp and I can swap in whatever chip I want. I like these a lot. I got two of them running 50W LEDs.

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