Great thread attml and long overdue! This issue is regularly debated and hopefully we could all chime in hear and come to an agreement. The reason I say that is because I think all of us are on the same page here. Let's try and simplify things, because I honestly think this is not as complex an issue as it's sometimes made out to be.
Let's start with some common denominators we could all agree on. I will not get into PAR or wavelengths because that is not relevant. More important is the penetration of each of the types of light into the water column.
NO fluorescent bulbs penetrate less than PCs which penetrate less than METAL HALIDES which penetrate less than the EQUATORIAL SUN. We can all agree on that I hope.
Now let's take a given intensity, and call it X (oh my God I'm using something from high school
). Let X equal the intensity of light on a given coral reef at say 20 feet depth where some of the beautiful sps we keep come from, but more importantly let it equal also an intensity where sps will thrive. These numbers are just for arguments sake mind you. Whatever the depth, there is a quantifiable number where we will find X in a metal halide tank. Let's say 1 to 2 feet. Obviously there are a wide range of factors here, including bulb wattage, spectrum, reflectors, and the height of the bulb above the tank. (In regards to the latter look at Sanjay Yoshis studies on the penetration of metal halide lighting into the water column. The difference between mounting the halide 6", 9", or 12" above the tank is larger than most people would believe. Anyway sperate issue).
Then let's go to a PC bulb. X will still be found in PC bulbs, but much closer to the source... say between 0 and 6 inches. Please don't argue the n umbers themselves as they are purely for argument's sake.
In the NO fluorescent X would be somewhere inside the bulb let's say
.
This is where my tank and Deezreef's tank fall in. All of the thriving sps and clams are within inches of the PC because they are 10 gallon tanks. Is the success simply because it's a 10 gallon. No. It's because the specimens are within inches of the PCs. Would this work in say a 75 gallon? Only if we piled live rock up to the top of the tank and directly under the lighting, which no one does because it would essentially be turning your 75 gallons of space into a live rock tank
.
That is why we could all agree that those wishing to keep sps, clams, or other high light corals in larger tanks should use metal halides. Frankly I recommend halides for ALL larger tanks, regardless of specimens. With that said I also think when we start out in the hobby we should stay away from sps and clams regardless of lighting, as they are hard to keep for many other reasons. But, if experienced enough to provide a stable and as-natural-as-can-be living area, many sps are pretty hardy I believe.
attml you show a perfect example of light starvation, as there is one thing that seperates this example. Many people throw up pics and say "Look, my sps died and I have PCs... sps NEED halide." In Eric Bornemann's Aquarium Corals book (a must-have IMO), he mentions that die off can be caused by many things, and a lot of times from deteriorating water quality (which in itself could be 100 of things). However, it's easier to blame the lights, as that is so commonly the case. Lighting IS SUPER important, but so are MANY other issues. Anyway, all you changed is the lighting and the acro came back, so that is good evidence that the PCs were not doing it for the coral, which goes back to my first point about penetration.
attml I also completely agree on your point regarding people seeing my of Deezreef's tank and believing that PCs can keep sps under any conditions. That's unfortunate, but we can only help those who are willing to listen. I've said these things time and time again...
1. Nano-reefs are in general harder simply due to the fact that when something goes wrong, it manifests itself much faster, and so only those experienced should attempt them IMO. Yes beginner's could start out with them, but at a much slower pace and with more research.
2. Even if you aren't considering a reef tank, I recommend halides to all (even the novice as eventually you will want to upgrade, unless you're in the small percentage that DOESN'T get addicted to the hobby
).
There are very few blanket statements in this hobby, as in "sps need halides." In most all cases that is true, but NOT all. I set up my 10 gallon after I got married because there was no way I was putting my 180 TEMPORARILY in the apartment my wife and I are renting. The 10 will be much easier to move, which will come later this year or next year, in which case my 180 will go up and house many of the small frags and clams I have in my nano. I did not have room for a halide due to the kitchen cabinets, and did research including looking at Deezreef's tank. Anyway I've gone way long, and won't bother to post pics of my tank unless requested (I have plenty of examples). Instead refer to the
www.nano-reef.com homepage and follow the link to my tank by clicking on the pic.
Let's go back and forth on these things here... but please keep the bashing down and the arguments mature and backed up by facts. Please don't give examples of how you know people who have failed, as I am not argueing that. I'm just saying there are circumstances where they could thrive under PC. Read my recommendations on halides though, I am supporting them for all who want to keep these animals, with the exception of experienced reefers who are keeping nanos.
Anyway... I'm spent
Johnny
