08-23-2019, 08:02 AM
Join Date: Apr 2005
Location: Brentwood, CA, USA
iTrader Positive Rating: 100%
| | Re: Needing expert advice on lighting for low to medium light plants.
That is a standard 55 gallon tank. "Breeder" tanks are not that tall - usually about 12 inches tall. I will always suggest that people spend about $25 on a digital lux meter, like https://www.amazon.com/Dr-meter-Upgr...xpY2s9dHJ1ZQ==
which are sold on several internet stores. That lets you measure the light intensity in lux, not PAR, and not in water. You can prop up your light so the meter sensor is the same distance from it as the substrate will be, measure the intensity in lux, divide that by 70 and you will have a crude estimate of the PAR you should get at the substrate level. A good PAR value would be about 30-40 (2000-3000 lux) for low to medium light plants.
LED lights tend to have a very large spread, so a lot of light can reflect off the glass back into the water, if the glass is clean on both sides. I have seen as much as twice the PAR in a water filled tank than what it was in an empty tank. That isn't sustainable, because the glass is never 100% clean, but it does show that the reading in the air is less than what you get in a water filled tank.