The Shrimphaus gets some light brown coloured algae-like material growing on the glass which needs periodic scraping off. It won’t just rub off casually, but it comes off using a credit card blank relatively easily. It does seem to happen more in regions of higher lighting. It isn’t super unsightly, and doesn’t happen fast enough to be really bothersome, but still. I suspected diatoms (because of the brownish colour) which are pretty common in new aquaria. Reputedly diatoms are a “problem” that pretty much solve themselves over time, but seems not the case for the quite well-established Shrimphaus – these happened in the previous iteration of the Shrimphaus as well.
diatoms on glass
scraped off diatoms
I asked around on UKAPS and the general view was ‘too much light’. Well, that is certainly possible, although diatoms never happen in the high-tech Fireplace Aquarium which has always been lit up more brightly. I did some reading on diatoms and they are a type of algae that looks brown because they have an extra light-absorbing pigment in their chloroplasts, fucoxanthin, which absorbs green light as part of their chemistry of converting visible light into biological energy. This is of course very different from chlorophyll, which absorbs both blue and red light, but not green – this is why green plants look green: chlorophyll absorbs the other colours. Turns out there is a lot of interest in fucoxanthin with potential applications in food, cosmetics and medicine.
Trying to reduce diatoms by selectively reducing green light
So it occurs that it might be possible to inhibit the growth of diatoms but not the other plants in the Shrimphaus by selectively turning down the intensity of the green LEDs in the Week Aqua light the Shrimphaus is using. I had this on the preset mode ‘Red’ setting previously which actually has quite a lot of green in it. I turned the green down a bit, turning red and mostly blue up to compensate and keep the overall power of the lighting constant. This gives the Shrimphaus a much ‘cooler’ looking lighting profile.
| 'Red' preset mode | Reduced green | |
|---|---|---|
| R: Red | 22% | 21% |
| G: Green | 24% | 20% |
| B: Blue | 15% | 20% |
| UV | 31% | 31% |
| Fan | 100% | 100% |
| Power | 30% | 30% |
It’s not any kind of controlled experiment, but let’s see what happens and whether turning down green can promote the growth of green plants whilst inhibiting diatoms.
Week Aqua ‘red’ lighting
green LEDs reduced