So when I kicked off my tank I had 2 250 watt 10k Mh bulbs over a 6' 155 gal bow front. Corals stayed brown with little color so I figured I'd not have ANY question on the lights. I ordered 3 400 watt Radium bulbs with necessary ballast and mini reflectors. I started the reflectors 18" from the water which I figured would be plenty high enough. After having the lights for 4 months or so the corals weren't growing, my acan bleached out and was really unhappy. Clam loved it, though. I measured that even at 18" (bulb) height, the PAR was 300 on sand and over 500 near water. So the acros were getting over 300 and my birdsnest was getting blasted at 350. So, I raised the lights some more. Now I get like 180 on the sand with top of tank at 300. My acan is definitely happier (I also moved him to the side of the tank to get less light). The light didn't "look" bright to me, and I would have never guessed I had too much or that it was too bright from the 10k's. If you haven't used the PAR meter, might be worth doing. According to this, once you get past the photoinhibition point the coral begins to basically shut down (or at least, isn't useful for coloration so going past that isn't really needed). So in my set up I absolutely could introduce too much light for many species. http://www.advancedaquarist.com/2007/3/aafeature1 Salient quote: At this point, it seems that zooxanthellae/hosts requiring really intense light generated by higher wattage (250-400w) lamps are the exception instead of the rule. ‘Blasting’ corals with light could actually inhibit photosynthesis and possibly slow their growth. Basically I spent a lot of money on lights that I didn't need to - I succumbed to the "radiums are awesome" posts. While I'm not ready for LED yet (I don't need to worry about heat and I'm not quite there on the $ honestly). Maybe I just need 2 lamps instead of 3. I'll have time to worry with it later. Also with the blue of the radiums they all but eliminated the reds and purples. I've put 2 purple T5 bulbs to balance them out. Still don't like it. But I will say this - with the lights higher off of the water I know I don't get the heat transfer to the water I would otherwise with them closer - so that may be a bit of a tradeoff with having a higher wattage lamp higher up vs. lower wattage closer to water. Savings in $ with electricity? Probably not. I'd just think temp stability would be the tradeoff if heat is ever a consideration.
Yeh, it took me awhile before I convinced myself to buy a par meter. Got one on black Friday 2 years ago or so, the BTM 3000 par meter. Was running the gen 3 radions at 35% and was producing around 120-155 par on the sand. It was actually too much for what I keep. I was watching one of the photosynthesis lectures for sps corals and at around 150 par, some of the hard corals were under going photo-inhibition. However, I wouldn't be too surprised if some corals did do well under 300+ par but definitely not for the inhabitants in my tank. I think having access to a par meter is a must in this hobby.
You have to balance the light/nutrient ratio in your tank. The higher the light the more available nutrients as well as calc/alk will need to be available for growth. I read long ago on a method called The Blu Coral Method, that is not mispelled either. The Italians use it and I've used it in the past with great success and a LOT of dosing. It's not for everyone but the main idea is elevated levels of everything makes coral grow faster. That said if all levels aren't raised it can be detrimental
Huh - have to look that up. I've read that folks that carbon dose (me) have improved results with lower Alk (than they typical 9+). And I can say that as I've gone through trying to improve things I've noticed that the corals are happier with alk closer to 7-8 than any higher than that. And I can say this: I have a healthy vermetid snail population in the tank so I have to think there's enough food going in to keep everyone happy. Even when NOT carbon dosing I've not detected any N and P on my tests - but I started carbon dosing anyway. Could things be even better? I'm sure they could. But I'll tell ya, since I reduced the light intensity the corals have definitely perked up.
Whenever you achieve that balance and stability just keep on doing what you're doing! There are many ways to grow coral, don't let anyone tell you otherwise
