Id like to ask what the definition of low light and high light tanks are?
Say in terms of lumens or lux or whatever the method of measurement and how that translates to tubes or bulb type lighting.
This is my opinion on low light/high light. This assumes normal output flourescents. Low light 1.5 - 2.0 watts/gal. Med light 2.0 - 3 watts/gal. High light over 3 watts/gallon. My definition is not based on growth rates, but on the level of light at which the management of a tank becomes more complicated. My favorite tank so far is 2.0 - 2.5 watts/gallon with co2. You can grow lots of plants, get good growth rates, and have fewer problems with algae. I am amazed at the number of people new to plants who have lights in excess of 4.0 wpg. At that level you better be an expert.
The watts per gallon required for low, medium and high lighting depends on the light type being used too. AH Supply kits are, in my opinion, very good both as to the bulbs and to the reflectors, so less watts per gallon are required with them than with T8 fluorescent bulbs with white painted flat reflectors. And, the watts per gallon also depend on how high above the tank the light fixture is. The higher the fixture, the more light is lost due to spillover. (If the reflector is reasonably good, and the bulb is down in the reflector far enough, the loss of light by the square of the distance is not the most significant loss.) So, in my opinion again, it isn't really possible to say how many watts per gallon equal high, medium or low light without also saying a lot more about what lights and how they are mounted with what reflectors. I think that's why the watts per gallon "rule" is nothing more than a crude ballpark estimate of the amount of light needed.
Vaughn that I guess is why Im struggling a bit with making my mind up on what I need ,Not only the type of light but the distance from the tank. I think Ill setup a 2 ft tank to start with so I can make it a fry tank later on. It also means less equipment to start with as my budget is quite tight atm.
As Im not sure whether the tank Ill get will have a hood or not I think I'll make up a hood and have adjustment for the lights built in to it.
Thanks Henry those yardstick figures are ideal for starting up a new tank .
If you know the lumen output of your ligth you can recalculate it to lux, using the height from lamp to bottom and area of the tank, if the lamp is on top of the tank, you can use the volume of the tank:
Lux = 1000 x lumen/ vol (L)
I use these standards to compare the lighting:
Low - 10000-20000lux
Medium Low - 20000-40000lux
Medium - 40000-60000lux
Medium High - 60000-80000lux
High - 80000-100000lux
Somewhere i read that direct sunlight on a clear day was rated to 100000lux, and i used the low 10000lux as given from a standard 15W floresent (apr. 500lm) in a 54L tank.