Leggy plant growth - General Aquarium Plants Discussions

Bryeman · 11-02-2009, 04:43 PM

I have a 125g aquarium with about 31 species of plants currently. Everything has been growing great and there is no algae in the tank except for the spot algae that begins to appear on the glass and a few leaves of slower growing plants like my Anubias. Both species of Cabomba (carolina and pulcherrima) are getting "leggy". They have great stems, but I'm seeing up to 3-4" between nodes at times. None of my other plants have this at all (L. indica is next to carolina and is not showing same behavior).

What causes this? Is it lighting primarily (too much, not enough for this specie), or something else? I EI dose, and given lack of algae outbreaks in the 2-3 months I've had this tank, I think I have the levels nailed pretty good. Lighting is 8x39w of T5 HO lighting, only run 4 bulbs at a time with a 3 hour burst/overlap period in the middle. Bulbs are Aquaticlife (love the fixture, not sure about bulbs though) 2 - 6500K, 2 - 10,000K, 4 - Roseate. Any thoughts would be appreciated.

davemonkey · 11-02-2009, 06:40 PM

Got a picture of the leggy stems? And are these reaching the near the top of the tank yet? Legginess is normally due to low light levels. 4 bulbs gives you about 1.25 wpg on a 125, which I'd call moderate light, BUT, the tank is deep enough that the light is a fair amount weaker near the bottom half of water depth. I'd bet (unless they are already there) that as they pass that half-way point, the stems get less-leggy.

Maybe try bumping the burst/overlap to 4 hrs rather than 3.

-Dave

Bryeman · 11-02-2009, 07:07 PM

They reach the top in about 5-6 days usually. They do get shorter length between nodes right at the top as they bend and grow along top of water. I usually trim them and keep the top 1/3. They don't grow much for 2-3 days, and then in the next 2-3 they'll shoot to the top.

davemonkey · 11-02-2009, 07:13 PM

Yeah, sounds like the lighting. Try the longer period of burst and see what that does.

wi_blue · 11-02-2009, 07:15 PM

I would say your Cabomba would like more light. I have some hydro that is growing long between nodes. It grows fast though likes higher light levels than I can give it right now.

Philosophos · 11-02-2009, 07:32 PM

I'm of the mind that it's not so much high light, but uneven light that causes leggy growth among other things. I've got some wonderfully dense plants in a <1 wpg tank with some space given to them, and had the same species show miserable growth under high light with bad spread or dense growth. That being said, it does tend to be easier to get uneven light in lower light conditions.

Interspecies competition can cause leggy growth, stunting, melting and all kinds of side effects; keep an eye out for it and test for the possibility when you see strange things happening in dense portions. Most people in the hobby have observed this competition at some time or other when they look for it. Here's a thread on the subject of interspecies competition with some decent studies to go with it:
http://www.barrreport.com/articles/6...mpetition.html

Higher current can also give you more compact growth. It's not so much that it's a requirement of dense growth, but it helps. The current its self likely makes it advantageous for the plant to retain a shorter growth span in order to decrease the level of pressure exerted on it. Much like high light, it has been observed that plants focus their growth efforts where there are high levels of nutrients. This is the sort of thing you'll find a fair bit of research on, but here's something to get you started:
http://www.jlakes.org/web/Interactio...hyte-H2001.pdf

I've found the principles of compact growth are really very similar to the concepts behind healthy growth. As of late I've been looking at one as an indicator of the other, and it's proven out a good part of the time. Try messing around with these parameters and observing it for your self.

-Philosophos

armedbiggiet · 11-03-2009, 05:30 AM

I would just try to burst longer...

Bryeman · 11-03-2009, 12:54 PM

I'll try the longer burst for now and see what that does. Also, the Roseate bulbs appear very dim compared to the 6,000K type bulbs. Is this just a visual thing or are these "specialty" type bulbs really more dim? All of the other bulbs I have besides the 6,000K appear dim. The 10,000K would be the next visually "bright" light, but the Roseate is dim. Just wondering what this does for plant growth. I thought my plant growth was good, but now I'm second guessing myself. I only have the two 6000K (I originally posted 6,700K, but that was wrong) that I consider visually "bright". The other 6 bulbs are Roseate or 10,000K. I noticed in a pet store some Hagen T5's. The 6700K had a lux of 300+ while the 18,000K had a lux of 140 or something. Seems like a huge difference but not sure what lux really means for plants (if anything).

Bryeman · 11-03-2009, 01:12 PM

Quote:

Originally Posted by Bryeman

I noticed in a pet store some Hagen T5's. The 6700K had a lux of 300+ while the 18,000K had a lux of 140 or something. Seems like a huge difference but not sure what lux really means for plants (if anything).

Nevermind, I went back and read the lighting stickies and figured the lux thing (perceived brightness versus what's happening with plants).