Bulb Anemone

[AndyS]

Plus one bulb is actinic, and provides no useful light for corals or anenomes, so that cuts down on your watts instantly.

Andy

 

[SkiFletch]

Plus one bulb is actinic, and provides no useful light for corals or anenomes, so that cuts down on your watts instantly.

Andy

Not entirely true Andy. Yes actinics put out less PAR than a 10000k or "daylight" tube, but its not like they're completely inept at outputting usable light for corals. Obviously each tubes, reflectors, and setups are different, but the PAR values actinics put out are typically ~1/2 that of their daylight counterparts. Even still, the wavelengths the actinics do put out are different than those of 10000K's and may be more beneficial to the chloropolasts of certain zooxanthellae. There's unfortunately no way to know which specific wavelengths your corals/inverts require, hence we aquarists try to do a mix of 10k and actinic

As to the 70watt halide vs 65watt PC question; If both fixtures use reflectors, then the halide will output MUCH more PAR down on the tank. Both lamps physically put out similar PAR from a quantity standpoint, but the construction/design of PC's inherently wastes a lot of that light. Much of it bounces in between the tubes next to it and does not reflect down on the tank. Furthermore, some bounces up, hits the reflector, and then encounters the other tube next to it. As such PC's can waste a lot of usable light, and that is why I usually consider them to be low-light options. Affordable for sure and useful for softies and LPS, but not great for much else. Halides on the other hand have a very small point-source of light that doesnt get impeded on its way out of the tube, and most reflectors are very good at pointing the light back down on the tank.

While we're talking lighting, let us not forget T5HO. T5HO tubes with individual reflectors can be as effective if not more effective than Halides (especially if they are overdriven via an IceCap 660 ballast or similar). Because it is a single bulb and a single reflector, the light is reflected down on the reef much better than PCs even though the tubes are nearly chemically identical. All about the reflector . In fact, let's take a hypothetical 90 gallon reef tank. A 6xT5HO lighting fixture will actually output nearly the same PAR to the corals than a 2x250watt metal halide system and more PAR than a 2x175watt halide. My club's been measuring PAR values in people's tanks with a PAR meter and been finding this to be true so far.

One last piece of food for thought. While T5HO might be a great option, their hardware cost of operation is steep. Buying ballasts, wires, reflectors, and bulbs for 6 T5HO's gets expensive fast. Replacing bulbs is also very expensive. With a Halide system, just one or two of everything... If in the end the wattages are nearly the same, the T5HO's will cost more to operate than the halides because of the increased hardware price.

 

[Musho3210]

But remember T5 HO dont need to be replaced as frequently as MH. Lets say a 48 inch tank has 6 T5 tubes, then another identically sized tank has 2 175 watt bulbs. 15k XM mh bulbs go for 60 dollars and you replace them every 8 months. Within two years you spend 360 on MH bulbs. With T5 you have 2 10,000k and 2 actinics that go for an average of 23 dollars each. 23x6 = 138 dollars and you replace these once every 2 years, after two years you spend 138 dollars. As you can see 138 is less than 360....


T5 has a more even par, lets say the T5 par is 100 everywhere in the tank, and the MH has 500 PAR near the top of the tank and 20 par at the bottom corners. In the end they both average out around the same amount so you can say they have the same PAR, but under the spotlight of the MH will have more par since all the light is coming out of one confined area where all the PAR is concentrated but with the T5's, the PAR is spread out. This can be a benefit and a bad thing since with MH you can have light demanding under the spotlight and not so much light demanding in the corners, but if you want all light demanding that may prove to be a problem. Plus T5's dont have the shimmer effect. I dont see a clear winner and both have an even amount of pros and cons, they are both great lights. PC's are T5 tubes but almost everything else in PC's are different than T5's, phosphors, heat etc. So PC's have been put down, plus you lose light with PC's as was said before.

The T5 vs MH is a highly debated topic and now LED's are coming into the debate, but remember LED's price is T5 combined with MH then multiply that by 2....

 

[SkiFletch]

Again, a common myth amongst aquarists regarding bulb life, and part of the problem lies in the ballast chosen to drive the bulbs. Using an overdriving ballast for T5s OR for MH's will drastically shorten bulb life span. We've been observing in our club output decreasing to 70% in one year's time on T5s or MHs overdriven. However if you run either T5's or MH's on more conservative electronic ballasts we've seen 85% light output on 2 year old bulbs. In fact Sanjay Joshi has been recently suggesting replacing metal halide bulbs driven by electronic ballasts once every 4-5 years... One member of our club whose been keeping HUGE carpet anemones for the past 14 years just replaced his 250watt Iwasaki bulbs driven off IceCap electronic ballasts after 6 years. The bulbs were down to about 68% of their max (brand new) output at that time yet his tank was as flourishing as ever.

Bottom line, you're right, there's no clear winner and each tank and design should have it's own lighting system designed for the needs of the planned livestock. But unless overdriven, our bulbs will last longer than the manufacturer (who wants your money) says they will...