Is there a such thing as too much LIGHT?

[sldp999]

hi,
i was wondering if there a such thing as too much light for a fish/planted aquarium?.
i have a 20 gallon tank with some fish and a whole alot plants, running pressurized CO2 AND i recently both 2 light fixtures which have 2 T5HO blubs each. (that is 4 Blubs in total). the back light fixture has aqua glo LIFE which is 24watts each and 6700K each. the front fixture has 1 aqua glo Life again and the oher blub is aqua glo POWER which is 18000K. that is a total of 96 watts. NOW i have them running for 12 hours but i take off the back light fixture on the 5th hour everyday.
IS THIS TOO MUCH LIGHT?
IF SO, WHAT IS THE BAD AND GOOD FOR ALOT OF LIGHT?

thank you.

[Alaris]

Too much light can lead to algae and a hot tank, especially if they're on for 12 hrs. Do you dose with any ferts? What is your level of CO2 in the tank?

[sldp999]

HI,
i only have one fixture for 12 hours and the other one is off the 5th hour. i have MASTER GROW for fert. and i have JBJ CO2 which has an automatic PH shut off controller and a 10LB tank.
thanks for your advice.
Take care.

[FishEggs]

it depends on the plants you have and how much you want to dose ferts and co2. if you're not getting algae or green water and the plants are growing then i'd say you're not getting too much light. just remember that the more light you have the faster your plants grow and use the nutrients which means the more you have to dose and trim the plants and the more electric you use.

i would try to simulate the sun a little better and turn the second light on a few hours after the first one and turn it off a few hours before the other one. you could probably cut back to ten hours and save some electric. just watch your plants and tank and it will tell you if it needs more or less light.

[OldMan]

One thing that may be saving you from some algae is that the 18000K light is treated by the plants as if it didn't exist. The spectrum is so far from a plant's needs that you are running efffectively only 3 lights for the plants. It is the same problem people have that run actinics, the plants can't use that wavelength effectively.