Dual 400watt halides above 75gal - too much?

2 250watt would be plenty 2 400watts would be way overkill

 

I agree, 250's would be plenty  but I would say of you can handle the heat and the utility bill go for it. I had 3 400's on my 125 and it had AMAZING growth.
If I had a 75 I would put 400's over it and run the canopy exhaust outside.
Almost as much PAR as the sun and great color too.

 

I had two 400 watt XM 20k's on a 58 gallon, and it was beautiful. I had good coral growth, but I also had a big electric bill from chilling and running the lights. One night my chiller went offline, and the whole thing overheated and crashed. Lots of risk. I now have two AI LED units. Amazing coral growth without the heat. Sold the chiller. Beautiful color.

 

Sorry to hear that.  There are many ways to prevent systems from overheating by using a controller.  When I had my "big boy lights" I had them set to shut off whenever the temp got above a set point as well as send me an email in case this ever happened.
There is some risk involved with using huge lights but if properly planned it is minimal.
I keep hearing about all this coral growth with the LEDS, yet I'm still not a believer.
  I am anxiously waiting for someone to prove me wrong however.  /DesktopModules/ActiveForums/themes/_default/emoticons/tongue.gif

 

IMO, quick coral growth is over-rated. My experience has been that it leads to a lot of problems (like coral running out of space, extreme chemical warfare, etc).

I think 400's over a 75 is definitely overkill.

-JB