HQI vs. Mogul
 

I am looking into upgrading the lighting on my 75. Probably going to be a system built into the canopy with a mixture of T5's and MH bulbs. Are there any advantages of HQI vs. Mogul bulbs over the other? It sounds to me like most people prefer the HQI version.

It depends on the wattage that you need. I believe HQI comes in 70, 150, 250, and 400... the mogul systems come in 175, 250, and 400 (and higher) watts. The mogul bulbs don't require a glass UV shield, since the bulb is already shielded. Note also that electronic ballasts will run bulbs whiter / bluer than either magnetic or HQI ballasts.

The lights in question would be for my 75. I will mostly be keeping softies and LPS but would like to try a few SPS and maybe a clam someday. From what I have read it seems to me that the mogul base would be the better system except for the smaller number of choices for bulb wattage. I am leaning towards a 250 watt system but it may be a little much for me. The 175 watt mogul sounds like a nive compromise between the 150 and 250. Is there anyone out there that is happy with their 175 watt mogul system?

Thanks
Howard

It is not "HQI vs. mogul" but rather double-ended (DE) vs single-ended (SE) metal halide bulbs. SE bulbs are also referred to as "mogul" which is what the socket they fit into is called.

"HQI" is a type of ballast, just like there are "electronic", "pulse" and "probe" ballasts.

HQI ballasts put out more light than other nominally comparable ballasts, but they also use a lot more electricity. For example, a true "250W HQI" ballast will pull upwards of 320W versus 250W for a "250W electronic" ballast. HQI ballasts can run all DE bulbs and most SE bulbs.

How do you tell what kind of ballast you have? Take off the cover and look for the ANSI code. For example, a 250W HQI ballast is an "M80". The exception is electronic ballasts which don't have an ANSI code, but distinguishable by being much smaller and lighter than other types of ballasts.

The main advantage of SE bulbs over DE bulbs is the amount of PAR the gets into the tank since SE bulbs do not require an extra glass UV shield that DE bulbs do. SE bulbs seem to offer a slightly greater spread, but DE bulbs are more compact for tighter spaces. SE bulbs used to have more selection, but DE bulbs (at least at the 150W and 250W formats) have caught up in this regard.

AH yes, I forgot that part... the bulb matches to the ballast. My ballast is M85, and so are the bulbs that I buy.

Just out of curiosity, then... do/can electronic ballasts run both SE and DE bulbs at the given wattage rating?

Another point to note is the higher the Kelvin the lower the PAR (generally). If you don't want light demanding corals, then be careful your lights aren't too powerful. My tank is 24" deep, and I can't keep my LPS any higher than the sand or they will bleach form too much light. My lights are 2x250w DE with 20,000K low quality bulbs (I'm trying to keep my PAR down so the LPS are happier!).

If you're happy with lower light SPS (Montis, Digis, deepwater Acros) and lower light clams (Squamosa & Derasa) then you may prefer to have T5HO lamps instead of MH or lower watt halides (like 150s). I'm assuming your 75 gallon tank is 21" deep.

Yes, it is the common 21" deep 75 gallon. I have considered T5's but always come back to the MH systems. After reading the comments here I am starting to lean towards a 175w SE system with a couple of T5's running actinic (I like to run the actinics 1 hour at dawn and dusk). I will most likely have nothing but LPS and softies as I like the motion of the corals in the flow. Might try the odd SPS but nothing serious. I seem to be liking the SE over the DE bulbs. I am screwed up here or not?

To answer your earlier question, there are people who overdrive their MH bulbs... I've heard of running a 150W DE bulb on a 175W ballast. Many electronic ballasts can 'sense' the bulb it's connected to, and will run the appropriate amount of power ie: a 175W electronic ballast will run a 150W bulb at 150W. I don't think this goes for all electronic ballasts, however, and overdriving your bulbs will reduce their life.

I would definitely go no less than 150W with that depth of tank, if you aren't planning anything beyond LPS and softies that should be enough (though PAR values may be a little low at the sandbed). Remember also that just because there are 25 extra watts at the bulb (from a 150W DE) doesn't necessarily mean that you will get that much more light out of your system, this has more to do with the bulb and ballast combination than anything... a 150W 10K bulb on the appropriate ballast could easily produce more PAR than a 175W 20K bulb on a magnetic ballast, though the same may not be true of that same 20K bulb on an electronic ballast.

I went through the same thing when I started my tank... I was originally going to go with T5s.

umm if it helps i have a 55g tank about 20" deep and use one 250W 14000k single end bulb on a probe start ballast and everything seems very happy from my zoas and shrooms up to my squamosa montis and digitata and everything in between i know very little about light just that this one seems to work for me! :D