Coral Growth????

[dendro982]

ProudMom:
I'm way down from your level of hardware, but, IMHE, you should have good coral growth, if I have it.
- May you list some common corals, that you have;
- what brand of test kits are you using (sorry about the question, but I had issues);
- how far are top corals from light (or post the photo - will be easier to talk);
- water flow: are shape or polyps affected by flow, like wind on the grass for GSP and yellow polyps, or flesh moved aside for LPS like candycane or blastomussa;
- quantity of food per day;
- if you have white xenia, what color is it (shade of color)?

I have good growth of common softies and LPS under PC (combo, 10,000 and actinic) from 18W over 6g, 110W over 90 g (intentional low light - my deepwater fish don't like more) to 72W plus sun over 10g. Have nitrates and phosphates because of heavy feeding. ~26x water turnover per hr.
What is growing reasonably well: white xenia, anthelia, GSP, BSP, yellow polyps, frogspawn, hammers, 2 types candycanes, 3 types of meat/open brain type of corals, blasto merletti and non-photosynthetic corals (some better, some almost no growth).

You may try to place some expendable frags into refugium, close to the top, onto chaeto - it will not take much place. In a couple of weeks you should see some difference in appearance. I know nothing about spectrum of metal halides, but in refugium yellow will be present.

 

[daytonians]

I am not trying to start a flame war here. I have to comment on some of the misconceptions that have been posted about light.

If you look at spectral graphs of halide bulbs you will see that 20K bulbs put out way more blue light than 10K. The spike in blue is on average about twice the power rating on for 20K verse 10K.

Still, a 10K bulb puts out much more light overall, since it is giving off light over much of the visible spectrum and not just blue. 10K or 15K MH with some actinic supplimation is a good compromise for most tanks but can differ depending on what corals you want to keep. Most people prefer the look of 10K or 15K over 20K also.

Secondly, blue light is NOT to make our corals look nice to us. Chlorophyll process light the best in the blue and red parts of the light spectrum. Since corals live under water the red part of the spectrum is filtered out, so they only recieve the blue part unless they live very, very close to the surface. I would not put large quanties of red light on a reef tank, because cyano bacteria can grow very fast under it. In short, our corals will grow best under blue light.

In responce to this:<I>
"If you place a 100w MH bulb over a 10gallon tank you get 10 watts per gallon. If you place it over a 100 gallon tank you get 1watt per gallon. But if the coral is placed in the same location under the bulb it will do fine in either tank."</I>

"Yes a coral place at the same distance from a bulb will do the same whether in a 10 gallon tank or 100 gallon tank. The far ends of the tank would get very little light though. That is fine if you are going for that effect. Most people are not. Remember the basic rule, light drops by 3/4 of its power ever time you double the distance.

Hope this is helpful.

 

[UrbanSage]

Very helpful and thank you for clearing up some of at least my own mis information.