Ummm - who the heck is Rex Grigg and upon what is he basing his facts? On that same page he states you can get by with less lighting on a 10 gallon because it's shorter than a 55. He contradicts himself, and an aquarium is NOT the same as sunlight over the tropics.
His figures appear not to take into account the depth of the water where the plants are growing in the tropics. Don't his high numbers for lumens in the tropics have to go down the 10-30 feet to reach the plants? I'd like to see where he obtained his facts and if they are based on lumens received at the bottom of the water not the top.
I'm not a scientist either, but I have had planted tanks for 20 years now and have grown plants in everything from high light levels of 5 wpg with CO2 to my current preferred level of 1.3 wpg with no CO2 added and plants simply requiring less light. The old WPG rule is just a rule - it can be bent and broken as much as you like, but it has served many long term plant folks well over the years. My books on aquarium plants list plants based upon WPG requirements (as well as nutrient, water temp, etc.), and they're right on the WPG recommendations about 90% of the time which is quite a good rate.
If this 5 gallon were set up with two 23 watt bulbs in a tight little incandescent hood we would simply have a fire hazard. That a lot of heat in plastic not designed to handle that kind of wattage over an acrylic tank which is also plastic. I used two 23 watt (or were they 27?) compact fluorescent bulbs over a 29 gallon tank using a modified plastic hood (ventilation holes doubled, fan added). Without the fan, it ran so hot the plastic from the incandescent hood went soft in a few places. Also, without CO2 and nutrient dosing his plants will die off because they'll outgrow the resources they need to survive.
Edit: One more comment. Anyone other than me try using the exact same WPG on a 20 long and a 29 gallon tank? I did, and I had to increase my wattage to keep the same plants healthy. 20 longs and 29 gallon tanks have the exact same footprint but the 29 is about 6 inches deeper.
Eric
His figures appear not to take into account the depth of the water where the plants are growing in the tropics. Don't his high numbers for lumens in the tropics have to go down the 10-30 feet to reach the plants? I'd like to see where he obtained his facts and if they are based on lumens received at the bottom of the water not the top.
I'm not a scientist either, but I have had planted tanks for 20 years now and have grown plants in everything from high light levels of 5 wpg with CO2 to my current preferred level of 1.3 wpg with no CO2 added and plants simply requiring less light. The old WPG rule is just a rule - it can be bent and broken as much as you like, but it has served many long term plant folks well over the years. My books on aquarium plants list plants based upon WPG requirements (as well as nutrient, water temp, etc.), and they're right on the WPG recommendations about 90% of the time which is quite a good rate.
If this 5 gallon were set up with two 23 watt bulbs in a tight little incandescent hood we would simply have a fire hazard. That a lot of heat in plastic not designed to handle that kind of wattage over an acrylic tank which is also plastic. I used two 23 watt (or were they 27?) compact fluorescent bulbs over a 29 gallon tank using a modified plastic hood (ventilation holes doubled, fan added). Without the fan, it ran so hot the plastic from the incandescent hood went soft in a few places. Also, without CO2 and nutrient dosing his plants will die off because they'll outgrow the resources they need to survive.
Edit: One more comment. Anyone other than me try using the exact same WPG on a 20 long and a 29 gallon tank? I did, and I had to increase my wattage to keep the same plants healthy. 20 longs and 29 gallon tanks have the exact same footprint but the 29 is about 6 inches deeper.
Eric
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