I have plants that requires strong light and currently, I have 2 of 65w bulbs = 130w. Both are 12,000 kelvins. I removed the two actinic bulbs that was also included and I am having another 2 of 65w bulbs with 6,700 kelvins on the way. All the bulbs combined will total 260w at 4.5 - 5.0 watts per gallon. Thats very high light, therefore the plants will benefit having CO2. I wasn't sure about a Goldfish tank, because I was told that Goldfish causes PH crashes with excessive Ammonia, etc. However, I do have 10x filtration and the water is ultra stable, so I think that a PH level of 7.0 should be fine for them. Its my first time using automatic CO2 system, which I have everything and it was originally planned for fully planted Angels tank. One night, I was working at Wal*Mart and I saw the cute orange Goldfish, so I got it. Now, the project for htis specific tank changed.