Elodea Densa, some of it brown at the bottom

[AlexT]

This relates to the plant being anchored in the substrate (sand) which mine is.

Is it normal for the lower parts of the stem to go a bit brown while the top is all lush green? I know it sounds a simple question in a way, because obviously at the top, that's where the light is. However, in my mind, I was assuming if one part of the plant is getting all the glory with the lights, aren't the benefits of that light passed down throughout the plant as "one being" so to speak?

However, in the way my tank is set up right now, it's like a jungle and needs sorting I think. I've got loads of elodea densa all bunched in around each other (which I quite liked initially) and I've also got lots of frogbit that's doing well and that's surrounding the elodea densa at the top.

The tank is 100cm x 40 x 50 (high). The lighting is x2 LED, one is 6500K and the other is 4425K. The lights are on about 10hrs per day and I use TNC lite liquid once per week for fertiliser. The water is 76F but has been between 80-84F recently due to quite extreme heatwave in London, now back down to 78F in the tank. The pH is 7.4 and the GH is currently 7 degrees.

How fussy is Elodea densa with lower levels of lighting at the bottom if there is good light at the top?

I tried to get some pictures but it's quite hard and none of the pictures looked useful as they don't really show the lower parts of the elodea densa.

 

[Byron]

This is why I have never bothered with stem plants much. Stem plants are fast growing, which means more light intensity and nutrients. All plants put their energy into new growth, that is their strategy. Some plants can even move what are called mobile nutrients from old leaves to new leaves to achieve this. The light entering the aquarium diminishes as it goes further down, and red light does not travel through water well at all, but blue does. So, the light reaching the bottom is certainly far less intense than at the surface, and it may be lacking in red (doesn't matter, I am certain that the distance is the issue which ever way). This is why most sources suggest periodically pulling up the stems, cut off the growing ends as far down as leaves are good, and replant.

 

[AlexT]

This is why I have never bothered with stem plants much. Stem plants are fast growing, which means more light intensity and nutrients. All plants put their energy into new growth, that is their strategy. Some plants can even move what are called mobile nutrients from old leaves to new leaves to achieve this. The light entering the aquarium diminishes as it goes further down, and red light does not travel through water well at all, but blue does. So, the light reaching the bottom is certainly far less intense than at the surface, and it may be lacking in red (doesn't matter, I am certain that the distance is the issue which ever way). This is why most sources suggest periodically pulling up the stems, cut off the growing ends as far down as leaves are good, and replant.

Thank you Byron, I might just do that, it doesn't look unsightly now, but it might down the line. Thanks for this. 80% of the Elodea does look nice. I've needed to trim it a LOT, it gets up to that 50cm tank height quick and easy. The lush green top parts I've snipped have been useful as a floating part in other parts of the tank that don't have any cover.

 

[Byron]

If you do not regularly trim stem plants, the tops keep growing and once they reach the surface will then grow across the surface, on and on. By this time there will not be sufficient light for the lower stems, unless you are running a high-tech system.

 

[sharkweek178]

This relates to the plant being anchored in the substrate (sand) which mine is.

Is it normal for the lower parts of the stem to go a bit brown while the top is all lush green? I know it sounds a simple question in a way, because obviously at the top, that's where the light is. However, in my mind, I was assuming if one part of the plant is getting all the glory with the lights, aren't the benefits of that light passed down throughout the plant as "one being" so to speak?

However, in the way my tank is set up right now, it's like a jungle and needs sorting I think. I've got loads of elodea densa all bunched in around each other (which I quite liked initially) and I've also got lots of frogbit that's doing well and that's surrounding the elodea densa at the top.

The tank is 100cm x 40 x 50 (high). The lighting is x2 LED, one is 6500K and the other is 4425K. The lights are on about 10hrs per day and I use TNC lite liquid once per week for fertiliser. The water is 76F but has been between 80-84F recently due to quite extreme heatwave in London, now back down to 78F in the tank. The pH is 7.4 and the GH is currently 7 degrees.

How fussy is Elodea densa with lower levels of lighting at the bottom if there is good light at the top?

I tried to get some pictures but it's quite hard and none of the pictures looked useful as they don't really show the lower parts of the elodea densa.

That's been my experience when I tried planting it. These days I just let it float.

 

[AlexT]

If you do not regularly trim stem plants, the tops keep growing and once they reach the surface will then grow across the surface, on and on. By this time there will not be sufficient light for the lower stems, unless you are running a high-tech system.

Just so I can be clear Byron, if it's all ONE stem and the top 50% of the stem is lush green and thriving, does the bottom end of the stem near the substrate still get short changed then if it cant get enough light, even though the stem itself is getting good light from the top? Thanks.

 

[Byron]

Just so I can be clear Byron, if it's all ONE stem and the top 50% of the stem is lush green and thriving, does the bottom end of the stem near the substrate still get short changed then if it cant get enough light, even though the stem itself is getting good light from the top? Thanks.

The leaves have to receive sufficient light and nutrients. The light reaching the bottom of the tank is much less intense and not sufficient for growth. Photosynthesis occurs in the leaves, and light is what drives it, so inadequate light and the leaf dies.

 

[Colin_T]

If the brown bit of stem is still firm and not squishy, then it's fine and natural colouration. However, if the brown bit is soft and mushy, then it's rotting. In this case you need to get a sharp pair of scissors and wipe them down with alcohol, then cut the plant about an inch above the rotting bit. Get rid of the rotten bit and carefully replant the good part.