[jnickerson1977]

I'm going to be setting up a 29g using the Walstad method. Judging by Hoppy's PAR graph, 2 t5ho is what i need. I know this graph shoots watts per gallon out of the water, pardon the pun. So... about the only lights i can find out there are 2x24 t5ho for my size tank. That will put me at 1.6 watts per gallon. I will be using 6500k daylight. IYHO, will this be enough, or will I need more?

 

[VadimShevchuk]

I have a 37 gallon 22"H and i use a Fish needit 4 bulb 24" fixture but i run only 1,3 row for 6 hrs with co2 and i had blyxa japonica growing like a weed. i think you should be fine

 

[Hoppy]

The Walstad method requires low light, never high light. A 29 gallon tank is either 18 inches high and 30 inches long, or 16 inches high and 36 inches long. To use even a one bulb T5HO light, with a good reflector, you would need to keep that light about 30 inches from the substrate. One of the one bulb hydroponic lights might be a good choice, but it would also need to be suspended high above the top of the tank.

 

[jnickerson1977]

Thanks for the info

I'm still waiting for my "Ecology" book to arrive. I did find 20W 6500k cfls at the store. Now i'm thinking about constructing a canopy. So many people say that only 40% of the light from a cfl gets to the substrate. So if I make a canopy with 5 20w cfls in it, that should be about 60 watts getting to the substrate? The only window I have to put the tank by is a north facing window. Here in AZ the sun is more intense, but we have triple paned, triple glazed windows. It's still a dimly lit room.

 

[2in10]

I'm still waiting for my "Ecology" book to arrive. I did find 20W cfls at the store. Now i'm thinking about constructing a canopy. So many people say that only 40% of the light from a cfl gets to the substrate. So if I make a canopy with 5 20w cfls in it, that should be about 60 watts getting to the substrate? The only window I have to put the tank by is a north facing window. Here in AZ the sun is more intense, but we have triple paned, triple glazed windows. It's still a dimly lit room.

Are those spiral CFL you are talking about? 2 or 3 would be plenty

 

[jnickerson1977]

Yes, its a GE spiral cfl 20w 6500k daylight. i have a 20g and a 30g that i need to light. with so many people saying that spiral cfls are totally useless for aquarium plants, i'm very confused.

 

[Hoppy]

See the sticky in this forum about CFL Power Saver bulbs. Just for information, you don't get any watts "to the substrate". Watts are a measure of the electric power used to light up the bulbs, not a measure of the amount of light the bulbs emit.

 

[jnickerson1977]

at first i was going by the par graph in the sticky. my 29g is 18" high and with my light 4" above the tank, even with AHS 96w pc, by the graph, i'll still be getting only low light. With t5 it shows that i'd still get low light.
The photos with the info on the spirals was helpful. Evidently I still have a lot of reading to do in order to wade through all the conflicting information. I'd rather not have to go through multiple experiments and waste my money before I find out what works.

 

[Hoppy]

at first i was going by the par graph in the sticky. my 29g is 18" high and with my light 4" above the tank, even with AHS 96w pc, by the graph, i'll still be getting only low light. With t5 it shows that i'd still get low light.
The photos with the info on the spirals was helpful. Evidently I still have a lot of reading to do in order to wade through all the conflicting information. I'd rather not have to go through multiple experiments and waste my money before I find out what works.

You are not reading the graph correctly. You probably have 2 inches or so of substrate in that 18 inch high tank, so if the light is 4 inches above the tank it is 20 inches from the substrate. At that distance an AH Supply PC light kit would give you about 40-50 micromols of PAR, which is medium light. A single T5HO bulb, with a very good reflector, would give you about 60-70 micromols of PAR, which is medium light, but higher intensity.

If you use screw-in CFL bulbs, the amount of light you get depends on the bulb wattage and whether the bulb is mounted vertically or horizontally, and whether a good reflector is used. If you use 25-27 watt bulbs in reflectors like http://www.homedepot.com/h_d1/N-5yc...splay?langId=-1&storeId=10051&catalogId=10053 you would get about 40 micromols of PAR, and it would take 3-4 of them to cover the whole substrate reasonably uniformly. The 6500K bulbs work very well this way.

 

[jnickerson1977]

Thank you for the clarification.