20 watt LED floodlight good for corals?

Maybe, maybe not- it depends on what exactly this light is. "Single module" does not directly imply it's a single diode; a module can have as many diodes as the manufacturer wants. It's for certain that it needs blue diodes (more blue than white, in fact) to achieve 14000K. As such, it could be comparable to the 18w PAR38 floodlights. If this is not the case, then I agree- it's a piece of crap; and more than that, the seller has crossed the line on false advertisement.

 

lol i really hope its not crap. that would blow

 

Sorry this is a terrible blanketed statement,
I'd also like to see your proof and experience on that. I use majority 14k leds on my tank and find they are much better looking than 6500k ones i used to have. I like my tank looking blueish so i prefer the higher chips versus the very yellow ones of 6500k.

You have to remember it all comes down to personal preference.

 

ok feeling a little better now about it...cool cool.

 

2:1 ratio of RB:NW, DR, TV, CB,and cyan
These lights have a pretty nasty spectrum and aren't very efficient.

 

When you use WW or NW you need more blues to get the same look with a 1:1 ratio of RB:CW. The difference is that your corals grow better because NW and NW cover more of the spectrum.

 

i like a little more blue also.

 

its only partly a matter of personal preference. there have been studies done oh what spectrum of light corals need to grow. and they measure that with a unit called pur (photosyntheticly usable radiation). and pur is made up of a few diffrent ranges of wavelengths most of which are in the blue range (420-470ish) so with if youre using white leds you will get growth because they way they make white led's is they take the same crystal that they use for blue leds and coat it with phosphorus. the phosphorus uses the energy it gets from the blue light to emit a slew of other colors, mostly yellow, which mix to give a white apparence and the ammount of phosphorus determines the kelvin rating of the bulb the more phosphorous the lower the k number and the whiter/yellower the light. anyway back to my original point because the white leds are made from blue diodes you still get pur out of them but not as much because some of that energy is used to make the other colors. and on top of all that you wont get very good coloration from your corals if you only use white light id throw in some other colors. and ive used the cheap ebay leds i had 2 of the 10 watt 10000k on mine for a few months and everything opened just fine and had ok color but then i added some blue and it looked much better and i got a little bit of growth. now ive had the radion from ecotech marine for over a year on the same 20 long and have had crazy amounts of growth.

 

So This torch coral I got Friday isn't looking good at all. It has a little brown slime disease this morning and the skeletons are showing some on all heads. I did a freshwater dip and it's back in the tank. I don't think it's gonna make it. I was actually debating on quitting the hobby since I can't keep anything alive in my tank. Seems like I have enough lighting and there is low flow. Params are good at: trates-0 trites-0 amm-0 sg-1.025 ca-450 alk-300. Only thing is I have a diatom bloom but my tank in 5 months young.

 

Your Alk is almost twice what it should be at. Get it down to about 150-175 ppm.

What is your flow in GPH? What is your light cycle? What is your magnesium? Phosphates?

Keep at it, your tank is still young and you'll gain experience and knowledge over time. You'll enjoy it in the long run.