Minimum light for plants

[DiscusBR]

Hi everyone,

I have a new 80g tank that is cycling. Tomorrow I am getting my plants, a few annubias and echinodorus. I will have not CO2. I have pool filter sand, but I will use planters to fix the few plants that will go in the substrate. All others (annubias nana) will be fixed in driftwood. My lighting fixture has two 54w T5 HO 6,000K lamps. My question is: what is the minimul ammount of hours/day that I should leave the lights on to ensure healthy plants but also prevent the development of algae in the tank?

Thanks in advance,

Mauro

[2wheelsx2]

If you want the plants to live, but minimize algae problems, I would aim for about 6 hours to start and watch the plants to see how they are doing. If they start developing new leaves then you know you have enough. If they are not doing well, then you can add an hour to the lighting period, but I have found that 6 hours is more than adequate for most low light plants.

[dbfzurowski]

Hi,
Two T5 HO lamps will give a lot of light. Like he said^^start with 6 hours.
Once you see which algae you will get, dose the missing minerals http://www.rexgrigg.com/Algae1.html

[Darrell Ward]

Good luck. I think you'll have algae (at the very least on plant leaves) no matter the duration. I would go with much less power, but with more efficient intensity. One 70 watt MH fixture with a 6500k double ended bulb, would work great if hung 8 to 12" above the tank. Might sound unconventional, but it works great. I struggled for years trying to light my 240 gal. tank with every fluorescent combination imaginable, and have a garage full of fixtures to prove it. Planted, and non planted, it didn't matter, it would still grow some type of algae until I changed the way I thought about lighting. After I hung 2-70 watt MH reflectors, 8" above the tank, all signs of any types of algae went away. I no longer have to wipe down everything in the tank at every water change unless I want to, and I can throw a few plants in there anytime I want, and they will actually live, instead of becoming an eyesore. Best of all IMO, is my wild discus don't even pay the lighting any attention, since it's not super bright, and shimmers around like natural light, instead of being bright and glaring all the time.

[Rlon36dr]

Hey there,

I would think it would depend on how the tank is shaped (i.e. how deep it is). If it is 18 inches, I would go with 80 watts of compact florescent, or 60 watts of T5, lighting. If it is a corner tank or other deep tank, I'd listen to the at least 70 watts of dangling metal halide suggestion. Best of luck!

[MacShadow]

I have kept planted tanks for many years. Currently have a 55g show tank with Discus and small tetras. I use 2, 40 watt bulbs, one Freshwater full spectrum, and one Marine full spectrum bulb. My plants do very well at 12 hours on/off. I have tried all different types of bulbs and wattages. The recommended formula of 2 watts per gallon resulted in algae blooms no matter what I tried. I have found that it is more important to change the bulbs every 6 months to get the right plant growth and control algae. Plants include Vallesteria, Swords, and Crypts. The biggest problem I have is pruning as the val tends to spread out into the open areas. I use under gravel filtration and an exterior box filter, temp is 84F. Most experts claim you cannot grow plants well with an under gravel filter, or at the higher temps Discus demand. I have been in the water/wastewater business for over 25 years and have found many unsubstantiated "facts" dealing with water quality and parameters in written expert material. Hope this helps.

[DiscusBR]

Thank you everyone for your replies. The tank has been running with plants for about 10 days now. I have a YouTube video with the setup:
http://www.youtube.com/watch?v=xyR-SXPQdnw
Here are some of my comments/responses:

If you want the plants to live, but minimize algae problems, I would aim for about 6 hours to start and watch the plants to see how they are doing. If they start developing new leaves then you know you have enough. If they are not doing well, then you can add an hour to the lighting period, but I have found that 6 hours is more than adequate for most low light plants.

Hi, Two T5 HO lamps will give a lot of light. Like he said^^start with 6 hours. Once you see which algae you will get, dose the missing minerals http://www.rexgrigg.com/Algae1.html

I have been doing 6 hours/day for a while now and the plants seem to be doing fine, although with some mixed results. One anubia and the echinodorus are thriving, with new leaves. One of the anubias, though, is doing poorly, with dying leaves. I don´t plan to use minerals. I am using instead these planters, which include small nutrient pellets:
http://hydrophytesblog.com/ripariums...6&product_id=5

Good luck. I think you'll have algae (at the very least on plant leaves) no matter the duration. I would go with much less power, but with more efficient intensity. One 70 watt MH fixture with a 6500k double ended bulb, would work great if hung 8 to 12" above the tank. Might sound unconventional, but it works great. I struggled for years trying to light my 240 gal. tank with every fluorescent combination imaginable, and have a garage full of fixtures to prove it. Planted, and non planted, it didn't matter, it would still grow some type of algae until I changed the way I thought about lighting. After I hung 2-70 watt MH reflectors, 8" above the tank, all signs of any types of algae went away. I no longer have to wipe down everything in the tank at every water change unless I want to, and I can throw a few plants in there anytime I want, and they will actually live, instead of becoming an eyesore. Best of all IMO, is my wild discus don't even pay the lighting any attention, since it's not super bright, and shimmers around like natural light, instead of being bright and glaring all the time.

Hey there, I would think it would depend on how the tank is shaped (i.e. how deep it is). If it is 18 inches, I would go with 80 watts of compact florescent, or 60 watts of T5, lighting. If it is a corner tank or other deep tank, I'd listen to the at least 70 watts of dangling metal halide suggestion. Best of luck!

It is hard to go with less power now that I have already purchased the fixture, unless I take one of the 54w lamps out. But 108w (two 54w lamps) for 65 gallons (final tank capacity) gives me 1.7 watts per gallon, which is the range often recommended for low-light tanks. Again, I will monitor how the tank develops. By the way, the tanks is 20 inches high.

I have kept planted tanks for many years. Currently have a 55g show tank with Discus and small tetras. I use 2, 40 watt bulbs, one Freshwater full spectrum, and one Marine full spectrum bulb. My plants do very well at 12 hours on/off. I have tried all different types of bulbs and wattages. The recommended formula of 2 watts per gallon resulted in algae blooms no matter what I tried. I have found that it is more important to change the bulbs every 6 months to get the right plant growth and control algae. Plants include Vallesteria, Swords, and Crypts. The biggest problem I have is pruning as the val tends to spread out into the open areas. I use under gravel filtration and an exterior box filter, temp is 84F. Most experts claim you cannot grow plants well with an under gravel filter, or at the higher temps Discus demand. I have been in the water/wastewater business for over 25 years and have found many unsubstantiated "facts" dealing with water quality and parameters in written expert material. Hope this helps.

Points well taken. As I said, I will monitor the tank to see if the 1.7 watts per gallon ratio will lead to algae. Hopefully I will not have the problems that you faced initially.

In summary, I will be doing 6 hours/day of lighting. If someone sees any problem with this plan, please let me know.

[2wheelsx2]

I have been doing 6 hours/day for a while now and the plants seem to be doing fine, although with some mixed results. One anubia and the echinodorus are thriving, with new leaves. One of the anubias, though, is doing poorly, with dying leaves. I don´t plan to use minerals. I am using instead these planters, which include small nutrient pellets:
http://hydrophytesblog.com/ripariums...6&product_id=5


It is hard to go with less power now that I have already purchased the fixture, unless I take one of the 54w lamps out. But 108w (two 54w lamps) for 65 gallons (final tank capacity) gives me 1.7 watts per gallon, which is the range often recommended for low-light tanks. Again, I will monitor how the tank develops. By the way, the tanks is 20 inches high.


Points well taken. As I said, I will monitor the tank to see if the 1.7 watts per gallon ratio will lead to algae. Hopefully I will not have the problems that you faced initially.

In summary, I will be doing 6 hours/day of lighting. If someone sees any problem with this plan, please let me know.

A lot of plants are grown emersed so you could have gotten one that is not adapting well to submersion yet and is dropping leaves. Anubias are tough as nails, it'll come around.

The watts per gallon rule was created as a rough guide. T5HO with efficient reflectors are almost 2x as bright as PC bulbs with poor reflectors, for instance, for the same wattage. I'm using currently 2x24w for 6 hours a day and plan to up to a second bank of 2x24 for another 4 hours once the plant mass is higher and I'm getting some algae even now, so I wouldn't say your tank is low light (my tank is a 30x30x24" cube, so about 100 gallons - 24" tall).

It's possible for it to be algae free, but you'll have to find that balance between biomass, plant load, and available carbon. Increasing surface agitation to maximize your O2/CO2 exchange with the atmosphere would help, and your root tabs (pellets) should help. I currently dose a bit of Excel and use these root tabs: http://rootmedic.net/

I think you may end up having to pull one of the bulbs for it to remain low light, but you can certainly grow plants without CO2 with even medium light as long as you find the correct balance. The only problem is that with high waste producers like discus, that balance is a lot harder to achieve than with say, a huge school of tetras.

[DiscusBR]

A lot of plants are grown emersed so you could have gotten one that is not adapting well to submersion yet and is dropping leaves. Anubias are tough as nails, it'll come around.

The watts per gallon rule was created as a rough guide. T5HO with efficient reflectors are almost 2x as bright as PC bulbs with poor reflectors, for instance, for the same wattage. I'm using currently 2x24w for 6 hours a day and plan to up to a second bank of 2x24 for another 4 hours once the plant mass is higher and I'm getting some algae even now, so I wouldn't say your tank is low light (my tank is a 30x30x24" cube, so about 100 gallons - 24" tall).

It's possible for it to be algae free, but you'll have to find that balance between biomass, plant load, and available carbon. Increasing surface agitation to maximize your O2/CO2 exchange with the atmosphere would help, and your root tabs (pellets) should help. I currently dose a bit of Excel and use these root tabs: http://rootmedic.net/

I think you may end up having to pull one of the bulbs for it to remain low light, but you can certainly grow plants without CO2 with even medium light as long as you find the correct balance. The only problem is that with high waste producers like discus, that balance is a lot harder to achieve than with say, a huge school of tetras.

Thanks for the detailed feedback. I think I will take one bulb out of the fixture. That will leave me with a 54w T5 HO 6,000K lamp for 65 gallons of watter. If someone sees any problem with this plan, please let me know.