I currently have a 5300K, 55W bulb with a CRI of 91 (Philips PL-L 55W/950/4P). When I made the change from a standard 20W fluroescent bulb, the condition of my 29-gallon tank changed considerably. Not only did the plants begin to grow as I expected, the algae also enjoyed the new found light. Since then I have managed to get the water parameters where plant growth is good without algae being a nuisance. I don't want to lose this balance.
My supplier does not sell this bulb anymore. My options are a 5000K or a 6700K bulb, both with a CRI slightly better than 80. I would expect the 5000K bulb to give a bit more of a sunset look while the 6700K may look more like noontime. My concern is how this change could effect the balance in my tank?
Other than a change in appearance, has anybody ever noticed a change in their tank conditions when you change the CRI or bulb temperature?
pH = 7.2 to 6.6 (high-pressure, manual CO2)
kH = 2 - 3
Nitrate <= 10 mg/L (AP test)
Ammonium = 0.5 to 1.0 mg/L in my tap water due to chloramine
Fertilizer = AP substrate and fish food, i.e., whatever comes out of the fish