wgoldfarb
Fish Fanatic
I just received an old Finnex 24/7 light from someone who is getting rid of his tank. This is the first time I have a light that allows you to customize the spectrum, which got me wondering if there is an ideal setting to promote plant growth while inhibiting algae, cyanobacteria or diatoms. (Diatoms are top of mind for me right now because I have a 29 that is about a month old and I have some diatoms growing on the substrate). I did some online research but wanted to get the thoughts of the more experienced people in the forum about what I found.
Disclaimer upfront: I know that the only way to truly control algae and cyanobacteria is through proper aquarium balance. I also know that diatoms are very common in new setups and will eventually stop growing on their own. This was more or less just an intellectual exercise driven by curiosity.
In terms of algae, It seems plants and algae can both use light in the blue and red (and far red) spectrums equally, so there is no magical combination of frequencies that would promote plant growth while inhibiting algae. I am not a biologist but this makes sense to me: since they both use some form of chlorophyll for photosynthesis (and Chlorophyll A, which is sensitive to blue and red, seems to be more or less universal), it makes sense that their needs would be more or less similar. Same goes for cyanobacteria, which also uses Chlorophyll A.
However, when it comes to diatoms, the story seems to be different. Diatoms have adapted to use very low light levels, so they can grow in low light conditions which would not be suitable for healthy plant growth. This would seem to be bad news. However, according to some research I found online (such as this article and this article, for example) diatoms require blue light to reproduce. So, I am thinking that reducing blue light relative to red light would allow plants to continue to grow, while slowing down diatom growth.
My next question was whether reducing blue light in favor of red could be bad for plants. I have seen some of the videos of Dr Bruce Bugbee (specially this one) which suggest that red light is used for overall growth (i.e. just growth in terms of total mass), and blue light light can control the shape of the plant by inhibiting expansion of cells along some dimension. For my plants, where I care primarily about growth rather than promoting a specific shape, it seems that reducing blue light in favor of red would have no adverse impacts.
So, at least on paper, it might be possible to somewhat slow diatom growth without affecting plant growth by reducing the amount of blue light. Granted, given the ability of diatoms to take advantage of low light levels you'd probably have to completely remove blue light, which might not be aesthetically pleasing. But could reducing blue light to some extent maybe help slow down diatom growth?
Thinking about it a bit further, one possible benefit could be aesthetic: currently, once the light turns off at the end of the photoperiod (which for me happens around 6 pm) it is harder to watch the fish and enjoy the tank. So perhaps I can leave the light on at relatively low levels of red until I go to bed (or maybe red-green, or even just green), which would allow me to see the fish a bit better in the evening but would not contribute to diatoms.
So, does any of this make sense, or there nothing to see here?
Disclaimer upfront: I know that the only way to truly control algae and cyanobacteria is through proper aquarium balance. I also know that diatoms are very common in new setups and will eventually stop growing on their own. This was more or less just an intellectual exercise driven by curiosity.
In terms of algae, It seems plants and algae can both use light in the blue and red (and far red) spectrums equally, so there is no magical combination of frequencies that would promote plant growth while inhibiting algae. I am not a biologist but this makes sense to me: since they both use some form of chlorophyll for photosynthesis (and Chlorophyll A, which is sensitive to blue and red, seems to be more or less universal), it makes sense that their needs would be more or less similar. Same goes for cyanobacteria, which also uses Chlorophyll A.
However, when it comes to diatoms, the story seems to be different. Diatoms have adapted to use very low light levels, so they can grow in low light conditions which would not be suitable for healthy plant growth. This would seem to be bad news. However, according to some research I found online (such as this article and this article, for example) diatoms require blue light to reproduce. So, I am thinking that reducing blue light relative to red light would allow plants to continue to grow, while slowing down diatom growth.
My next question was whether reducing blue light in favor of red could be bad for plants. I have seen some of the videos of Dr Bruce Bugbee (specially this one) which suggest that red light is used for overall growth (i.e. just growth in terms of total mass), and blue light light can control the shape of the plant by inhibiting expansion of cells along some dimension. For my plants, where I care primarily about growth rather than promoting a specific shape, it seems that reducing blue light in favor of red would have no adverse impacts.
So, at least on paper, it might be possible to somewhat slow diatom growth without affecting plant growth by reducing the amount of blue light. Granted, given the ability of diatoms to take advantage of low light levels you'd probably have to completely remove blue light, which might not be aesthetically pleasing. But could reducing blue light to some extent maybe help slow down diatom growth?
Thinking about it a bit further, one possible benefit could be aesthetic: currently, once the light turns off at the end of the photoperiod (which for me happens around 6 pm) it is harder to watch the fish and enjoy the tank. So perhaps I can leave the light on at relatively low levels of red until I go to bed (or maybe red-green, or even just green), which would allow me to see the fish a bit better in the evening but would not contribute to diatoms.
So, does any of this make sense, or there nothing to see here?
