Lighting for plants

[psychotic]

I bought some bacopa a few weeks ago because I read that eastern newts liked to lay eggs on it and it also didn't require a lot of light. However I guess my light was too low for this low light plant. All my bacopa turned mushy and decayed away into clumps of slime.

Anyway this time around I thought I would get a grow light or something. But looking online, grow lights are expensive. So my question is, could I use a reptile uvb/uva light (which is much much cheaper)? Would it keep my plants alive? I don't think it would harm my newts even though they don't require that sort of light.

Any suggestions of lighting that would help? My tank is on the bottom shelf of a book case and doesn't get a lot of natural light. Not even a lot of light from my room's light bulb. I have LED lighting on the tank itself for the low heat output.

 

[FrogEyes]

T5 HO flourescent lights, 6500K or 10000K color temperature will give you good plant growth and natural appearance. Add a bulb or two if you want floating water plants to do well. I find that duckweed does well with the combination of T5 HO, CFL/UV, and incandescent 'reptile' basking light.

 

[evut]

I have only one 25W T8 tube (Arcadia Freshwater) over a 90l tank and since I set it up with soil substrate, the plants have been growing like crazy. I've had no luck with Bacopa either, so I can't help in that respect. If you're interested in trying other plants, have a look at Ludwigias and Hygrophilas - they've done really well for me, with low light and very hard water.

 

[peter5930]

What you want is lighting that has high PAR/watt (Photosynthetically Active Radiation). I read an excellent analysis of the PAR efficiency of a wide range of lighting types some years ago, but I can't find it now. I do remember the important details from it though.

Unsurprisingly, high-pressure sodium lighting is the gold standard for PAR efficiency (which is why it's widely used in cannabis cultivation), but it's not something you want to use for your tanks; HPS bulbs don't exactly come in cheap, low-wattage varieties. Low-pressure sodium bulbs closely follow the HPS bulbs, but again, they're not practical for hanging over the typical aquarium.

Next up are the various fluorescent tubes; generally, T8 tubes are more efficient than T5 tubes and longer tubes are more efficient and last longer than shorter tubes. Surprisingly, the most efficient tube according to the analysis is the bog-standard General Electric T8 cool white fluorescent tube. It's spectrum isn't optimised for photosynthesis, so it puts out a lot of green light (which is the wavelength that the human eye is most sensitive to), but although plants can't make use of green light as efficiently as they can make use of blue and red light, the GE cool white tubes are so good at pumping out photons that they make up for the photons not being of an ideal wavelength.

A little bit less efficient, but still pretty good, are the pinkish-looking tropical T8 aquarium tubes. These put out a lot of their energy in the blue and red wavelengths, which is what gives them their pinkish look. The whiter-looking freshwater tubes are a bit less efficient for plants. There are also specialised tubes designed just for plants, like the gro-lux tubes, which give out a very dim (to our eyes) pink light, but they didn't score very well in the analysis I read. I don't know if it's a flaw in the methodology of the analysis, or if the company that makes them just hasn't been investing in R&D to keep up with recent developments in fluorescent lighting.

Don't bother with UV lighting; the only use it has is if you're trying to grow cannabis or basil or something and you want to trigger a stress response in the plants to make them produce more oil/resin to protect themselves.

Further reading:

Photosynthetically active radiation - Wikipedia, the free encyclopedia

GUIDELINES FOR LIGHTING OF PLANTS IN CONTROLLED ENVIRONMENTS

Lighting Duration, etc.

 

[kwarzym]

Does the switching over to a light with wider spectrum or higher brightness have a profound effect on plant growth/survivability? Or is it more of a recomended item? I was at Petco the other day looking at some plants and the guy there was insistent about me buying a special fluorescent tube for growing plants. At $19, I figured it wasn't going to break the bank, but I keep asking myself "Is it really worth it or is it just a placebo?".

I read some of those links, and while it does appear to be better for plants, do many of you get by just fine without them, or are they a must if you have a well planted tank?