Originally Posted by vi3tb0i
so your saying a 29gal with 130watts of PC lighting qouldnt keep a rose bubble tip anemone alive?
This is where the watts per gallon rule starts to suck wind. 130 watts (in my opinion) just starts to dip below acceptable wattage. I'd prefer to see about 220 watts over a 29 gallon as a minimum. Sure that 130 watts gives you 4.4 watts per gallon and usually about 4-5 watts per gallon is good when talking about 55+ gallons water.
Here this explains it better:
Lighting Banter and the Problem with
"Rules of Thumb"
By Eric Borneman
I have a pet peeve - "rules of thumb." In the last issue, I briefly mentioned one of the "rules of thumb" involving amounts of live rock used per gallon of tank water. In this issue, I would like to briefly discuss another rule that is frequently discussed and misused: watts of lighting per gallon. Some readers may have gleaned from threads on other forums over the years that this may not be the most accurate way to assess the lighting needs for reef aquaria. In fact, that is an understatement. Make no mistake, I was once a person who also subscribed to x watts per gallon, but I have long since learned the error of my ways - here's why.
Lighting is a critical component of any aquarium housing plants which require light for photosynthesis. The reader may ask, "But I thought the corals and other stuff in my tank were animals?!" Well, they are, but the coral animal couldn't care less about lighting - nor could those anemones, sponges, or other marine animals which may engage in photosynthesis. In fact, it is the symbiotic algae ( of many types) which they hold in their tissues that require the light. Therefore, it is actually plants who require proper illumination. This applies equally to macroalgae, mangroves and sea grasses (true plants), and even the frequently problematic pest algae and cyanobacteria (slime algae).
One of the first requirements of "proper" lighting is to assess the needs of the plants -- or animals, as the case may be. I am periodically asked the question "What lighting is best?" to which I am forced to reply, "There is no best. What are you keeping?" The reasons for this often unhappily met response are based on several issues which must be addressed to adequately assess lighting needs. The "best" lighting is one the meets or exceeds the requirements of the species present. It is not possible to simply "buy the best" and have it meet the needs of every tank inhabitant possible.
First, most photosynthesizers are adaptive - they can exist well on various levels of light. Other photosynthesizers are best suited to various, possibly specific, levels of low or high light. Others will only grow or thrive under certain light conditions and not others. Furthermore, some gain more from certain spectra of light, not merely being dependent on the amount or intensity. Generally, it is best to choose photosynthetic animals and plants which are either adaptable to the amount of light present, or to choose lighting based on the animals and plants which are desired. This way, they are able to easily provide themselves with various energy rich components of photosynthesis, which are then used for their growth and reproduction.
The second consideration is one of logic, albeit a logic rarely employed by the use of the "watts per gallon" rule. A simple example is all that is required to make the obvious even more patently clear. Under the "watts per gallon" rule, for instance, five watts per gallon has generally been assumed to be adequate for most reef tank inhabitants, with higher light corals, such as Acropora spp., requiring perhaps up to 10 watts per gallon. If one has a 10-gallon tank, then, three 18-inch 15-watt bulbs would put the aquarist darn close to an otherwise whopping five watts per gallon. A single 24-inch 95-watt VHO fluorescent light would nearly make the 10 watts per gallon. A single small 150 watt metal halide would put one at a tremendous 15 watts per gallon! Yet, who would attempt to keep Acropora spp., for instance, under a single lowly 150 watt metal halide? Few, I would imagine.
The point is that bulbs of any type emit a set amount of light. It matters not whether the tank it illuminates is 10 gallons or 10,000 gallons, three 18-inch 15-watt bulbs still will only put out the light of three 18-inch 15-watt bulbs. Conversely, if a coral requires the amount of light put out by a 400-watt metal halide bulb, that same bulb will be needed whether it be over a five gallon tank or a five hundred gallon tank. However, a 400-watt bulb over a five gallon tank will, unfortunately, likely cause tremendous heat problems on a five gallon tank -- unless, of course, the tank has use of a flow-through cryogenic cooling jacket surrounding it!
...continued on next post...