PAR increase 250W Radiums vs. 400 Radiums?

Michael Benz · Aug 2, 2018

I have 3 250w Radiums currently over my 375, I am ready to replace the bulbs. I was thinking about going with 3 400s for the change.

Here are the spec for my tank:
*250w Radiums mounted 18" AWL
*Top of Rockwork 27" from lamps, or 9" below water line
*Sand 43" from lamps or about 24" below water line
*Halides are on for 6 hrs/day
*4 80" T5's are on before and after Halides, ATI Blue+ bulbs

I tested when existing lamps were new with a borrow meter and it read about 350 PAR at top of rocks.

My tank is 42" front to back and it is setup as a peninsula, I have 8 Hydra 26 nearer the sides to reduce shading, they are set to about 35% right now, slowing ramping up.

Any recommendations?

Reeferdood · Aug 2, 2018

Will your ballast be able to run them or are you changing them too?
If you are going for a full blown SPS system then you can likely use more par..

jda · Aug 2, 2018

Compare PPFD of the following tests...

If you are using M80, then not much - 85 vs 93:

If you are not using M80 now, then a lot at 66 vs 93:

reefs.com/lighting and go to the "compare" link.

jda · Aug 2, 2018

The thing to watch on the 250 vs the 400w radium is that the 250w has a bit more violet/purple bump at 400-425. You can kinda tell if you have used them for a long time and REALLY know what you are looking at.

If you are you using M80 right now, then I would stick with the 250w and get some M80s too.

MIKE NY · Aug 2, 2018

I was in the situation a few years ago with my radiums.....until I found some Hamilton M80 HQI ballasts. Then I couldn’t justify the extra heat and electricity for a little extra PAR...so I stayed with the 250s....my tank is 27”deep.

mcarroll · Aug 2, 2018

Michael Benz said:
Any recommendations?

Unless there something wrong with the system, cancel these changes.

Maybe even roll back some of the changes already made.

2¢

Michael Benz · Aug 2, 2018

My ballast are the luxcore selectawatt ballast so I can go all the way up to 400 super lumens. It was not my intention to over drive them since I don’t want to have to replace them at 6 months. More concerned about too much light.

Breadman03 · Aug 3, 2018

Honestly, I'd stick with the 250's. You've got a lot of light available right now and the papers I've read comparing 250 and 400 pretty consistently showed more light per watt with 250's. Depending on your reflector spread, you could probably get a comparable PAR increase by dropping the halides a couple inches.

One thing to consider is that light on your glass grows algae. Maximizing light in the tank while reducing light on the glass will keep the glass clean longer.

Michael Benz · Aug 3, 2018

Thanks Breadman, I got the advice I wanted and will be keeping the 250s.Thanks

A. grandis · Aug 4, 2018

Michael Benz said:
My ballast are the luxcore selectawatt ballast so I can go all the way up to 400 super lumens. It was not my intention to over drive them since I don’t want to have to replace them at 6 months. More concerned about too much light.

You can change your ballasts for M80s. Having the M80 running your Radiums will NOT overdrive them, as you probably know, because they were actually designed to run with that particular ballast. You will get more out of it and will be worthy... Keep the 250s, yes.

gcarroll · Aug 5, 2018

250w Radium with M80 ballasts is my all time favorite combination. The PAR per watt is awesome and the bulbs will last up to 18 months. Unlike the 400w Radium, the 250w includes a nice bump in the actinic spectrum.

mcarroll · Aug 7, 2018

gcarroll said:
250w Radium with M80 ballasts is my all time favorite combination. The PAR per watt is awesome and the bulbs will last up to 18 months. Unlike the 400w Radium, the 250w includes a nice bump in the actinic spectrum.

Radium doesn't appear to be claiming the "extra hump" in their marketing. Very unlike marketing to not claim extra when they can.

250w:

400w:

Thoughts? What have you seen that shows different than this? (Just curious!)

jda · Aug 7, 2018

Check out the more detailed charts that I gave in post #3. Cleary a difference. You can see this with your eye as well... which is why people with lots of MH experience always ask about the ballasts being used with 20K Radiums before they give any advice, since the color matters. IMO, this is a pretty easy thing to see if you used the different ones.

gcarroll · Aug 7, 2018

mcarroll said:
Radium doesn't appear to be claiming the "extra hump" in their marketing. Very unlike marketing to not claim extra when they can.

250w:

400w:

Thoughts? What have you seen that shows different than this? (Just curious!)

As @jda stated, Sanjay's test data is what I based my info on. By the looks of what you posted, I am very disappointed that they would publish that. Pure laziness. It's like they used the exact same chart for both bulbs. They are clearly different per Sanjay's test data. Look how high the 400w blue spike is in jda's comparison chart. That is clearly not reflected in the charts you show.