Algae and Stunted Growth


Junior Poster
Dec 18, 2008
Hey everyone. I have been slowly tweaking my setup and have finally arrived with this and have had it running for about a month.

20 gallon high
2x24 watt t5HO fixture
Pressurized Co2
Eheim 2213
Dose EI as per the 20-40 guidelines posted here

Rotala 'nanjeshan'
Rotala rotundifolia
eliocharis parvula

I have noticed hair/thread algae growing on my plants, specifically when they are bunched closer together. It is brown/light brown when I pull it off, but it continues to come back. I have also noticed when I trim my rotala rotundifolia (I trim about 5-6 inches form the top when it reaches the surface) that where I clipped it turns dark, almost black, and does not regenerate. The leaves are all darker and less green then when I received the plant. I cannot seem to figure out what exactly it is that I am doing wrong. Th eonly thing I am not doing is adding a GH booster, I do not have a GH/KH test kit but I remember from using test strips a while ago that my hardness was basically off the charts.

Does anyone have any idea what could be causing me these problems?


Guru Class Expert
Jun 8, 2007
That seems like a wicked amount of light.... you could try raising the light several inches to reduce the intensity. T5 HO is very bright. You're probably in the range of 5 or 6 wpg of 'regular' light.


Lifetime Charter Member
Lifetime Member
Mar 12, 2009
I've had your exact problems, also with R. rotundifolia. Darker green means likely lower light conditions, especially if the leaves contract and the growth is more spindly. It's easy to plant this stuff so dense that it chokes its self out, too. As it grows in, you may find your self removing stems of it. This density can cause flow problems down low, which will encourage the kind of algae you're running in to. As for the trimming issues, get sharper scissors. Tissue scissors are good if you can get some, though non-serated micro tipped scissors for fly tying seem just as sharp.

48w of T5 is typical for high density 20 gal's; check out some of the AGA entries.


Tom Barr

Staff member
Jan 23, 2005
The 3 species are very easy plants to grow, and all will do poorly if the CO2 is off.
They can grow easily in a wide range of nutrients, that part is addressed, the light is plenty, so.........stunted tips and algae..........

Points to CO2 really.
Tank is a month old, you might consider adding Excel and doing more water changes until the algae goes away, make sure you have plenty of biomass, run lights for 8 hours etc.

Tom Barr