14k---20k

[squibley2]

I just bought 2 250W Mh pendents and will need to switch out the bulbs (which are 10K) due to a lack of actinics. Can I get a vote on 14K versus 20K for the replacements it will be some time before I get any additional supplimental light for the tank.

 

[bkv1997]

It is wierd and depending on the manufacturer you are going with it can even be more confusing. How much blue do you want and what do you plan on growing?

Picture comparison of some of the major bulbs
Reef Central Online Community - 250 watt SE MH lamps compared

Par spectrum comparison graphs can be found at this link
Sanjay's Reef Lighting Info Pages

I don know from local hobbiest/friends you want to go with the XM 20ks over their 15k always... I can't speak for the other manufacturers, as I personally use DE Bulbs... hopefully someone will jump in and help you a bit more.

Brandon

 

[squibley2]

Also comments on these?

eBay: 250 W Metal Halide 65k,10k,14k, 20k bulb Aquarium Light (item 220016217839 end time Aug-20-06 13:55:37 PDT)

 

[jhnrb]

Im in favor of the 14K, however, some like the 20K. Check out the bulbs spectrum spikes as not all bulbs are identical.

 

[bkv1997]

retracting post

 

[jhnrb]

Retracted post. follow bks links. you will get some very good information there. also be careful on the bulb you pick as some spike at different spectrums although the rating is the same.

 

[salt newbie01]

So let me see if I got this straight...When screwing in a mh bulb it can chage color depending on where you stop screwing it in?? If that is the case that's pretty cool because if you weren't happy with the color just rotate the bulb.?.? I am new to mh so I am just trying to understand, I had never heard of that before.

 

[bkv1997]

retracting post

 

[jhnrb]

Not exactly, i sent salt newbie a pm further explaining what i was trying to share. so to set the record straigt turning the bulb does not change the visual spectrum but the position of the inerds does and these can be adjusted by turning the bulb. hope this clears it up.

 

[squibley2]

I just ordered 2 Hamilton 14Ks. After looking around at all the different options the Hamiltons looked the best to me. So we will see how they work. I got a great price on them 49.99 each and shipping was about 10 bucks.

 

[bkv1997]

Those are nice bulbs... a club member uses them...

I think you will be happy with them. Remeber to acclimate your corals slowly over a couple weeks to the new bulbs.

Let us know how it works out.
BV

 

[squibley2]

The acclimation of the corals will be a little tough they are currently in my 20G with 130W or PC lighting and they are going to be moved into my new 55 with 2 250W MHs running the Hamiltons. So the acclimation will take some time.

 

[bkv1997]

If you can raise the lights up real high then slowly lower them that is one way.

Another way is to put 3 or 4 pieces of screen between the lights and the tank and remove a piece every 5 to 7 days.

You can also adjust the photo period and add to it slowly, but this is personally my least favorite method.

Brandon

 

[squibley2]

Why is adjusting the photo period your least favorite method? I would have thought that, it would be the easiest to do and the hardest to mess up.

 

[minireefer]

I would guess that it is do to the fact you will get less enjoyment out of your tank with the lights out

 

[squibley2]

Not if you set the photo period at night and then add backwards.

 

[bkv1997]

Blocking some light or moving the lights further away changes the intensity of the light hitting the coral... changing the time only means it isn't getting blasted with a light 5 times stronger than it is use to for a long period of time.

Just my opinion. Either will work though.

 

[Ironman]

BKV is right, best bet is to shade with egg crate or something, and gradually work your way to full light. Raising the light is also a good option if you dont have a canopy. That really is alot of light for a 55, im assuming you have softies and lps, due to the current power compacts. They will be more sensitive to the light change. if possible keep all the corals on the bottom of the tank for the first week to.
I also run 250 watt halides, im on my second year with 14k hamiltons and love them. i run some vhos to but they dont change the look much. you will be very happy with them. they also have a good par rating.
Good luck and keep us posted

 

[jhnrb]

Some shading is needed when you change to mh. advice already given is correct. you may also need to lessen the photo period also depending on how you shade the corals. I prefer the plastic light diffuser cut to sit over the tank but under the bulbs and add several layers offset to diffuse the light and remove one every several weeks or so. (only way to explain it is it is like walking out of a movie theater in mid day and cant see a thing until your eyes adjust, well corals take longer to adjust. if not properly adjusted you risk burning the corals, having them bleach, or expell their Zooxanthellate. hope this helps.