Lights, heat and efficiency

[mkt]

Hi

a newbie question - I'd been mulling about MH, T5HO and LEDs

if I install a MH 150W or a T5HO set 4 x 39 W, or even a 160 W Razor LED

Why does everybody says MH gives more heat? Presumably the wattage is the same( almost ) for all these fixtures. And MH normally provide greater intensity.

So what's the rationale saying LED is cooler etc? Is it more efficient?

[Shadow]

The light coming out from LED does not contain heat compare to MH or T5. LED still generating heat but at its electrode which is connected to heat sink. The easiest way to understand it by putting your hand under those light and you will feel MH hottest and LED coolest.

[David]

Hi mkt

I think you are going about it the wrong way. first lets break your question down to two parts mainly wattage and heat.

Lets start with heat.

The question of heat is important because to have (for a lack of better word) a nice planted tank heat within the water column is one of the key factor. Depending on the kind of plants you intend to have, a good temp range is between 25C to 30C...there abouts. Besides heat generated by the filter, heat generated by the lights above the tank is another.

It is for certain that of the three types of lights you mentioned of, MH produces the most heat due to the magnetic ballast. T5s depending on the number of tubes and wattage can produce a significant amount of heat as well but less. LEDs of the three produces the least amount of heat. Whichever the case, all (in my opinion and anyone using LED lights correct me please) will push the water temp above 30C after 8 hours of lights on timing.

Lets talk about wattage

150watts of MH is not equal to the 150watts of T5s is not equal to 150watts of LED. The WPG that we read about serves as a guideline rather than a rule of thumb. The difference here is light intensity. Of the 3, the light intensity of MH will be the highest followed by T5s followed by LEDs. Light intensity is important on two counts. First, how high you can suspend it away from the waterline for both aesthetics or plant-out-of-tank-growth, as well as heat control. Second how far can the light be thrown to the bottom of the tank after its height suspension. Lastly ease of maintenances of the tank, the higher the suspension the easier.

While the intensity of the MH is the highest, its intensity is more of a focused beam. This means that a high suspension is required in order to get a good light spread. On this count T5s are more forgiving as the light spread is more equal. LEDs like the MH is also more as a focus beam.

Another important factor is the CRI (Color Rendering Index) of the light source in question. If I am not wrong, most of them are pointing to its K (Kelvins) for marine tanks most of the lights are focused at 10K Kelvins that gives more blue, while plants prefer 8500 or 8600 Kelvins which produces more red. The choices of light tubes from many brands and its availability lays with T5s from most LFS. MH are harder to come by. LEDs, well I have no comment here as I personally have not tried LEDs.

Maintaining your lights is also an important factor. MH bulbs does not lose much of its intensity or CRI even after 1 year. I have personally pushed it to two years with no issues. T5s most likely will lose its intensity and CRI after 6 to 8 months depending on brand which means cost of maintenance is high for T5s over MH. Again LEDs I have no comments but judging from my LED downlights used in my home, its intensity dropped after 7 months or so?

So the choice is yours how you want to go about the big question on lights.

1. Your ability to keep the water column to the temp suitable or optimal to the plants kept.

2. The ideal height of light suspension over intensity of light to the bottom of tank.

3. Running cost and duration of bulb changing due to the lost of CRI and/or intensity of lights.

I am a believer of the MH. First for its ability for high suspension and low in-between bulb change. As I am also a believer of the chiller for temp control, heat is not an issue for me. As I am lazy to keep changing bulbs, T5s are also a good consideration and as I have seen the light sets available in the market, they are pretty good. The more expensive brands are even able to squeeze 6 T5s into a very small footprint keeping the light set look very elegant. But again, I am lazy so T5s will be my second choice. As for LEDs, again I have no comments as this technology is still relatively new in the planted tank scene compared to the MH T5s or even the PLs, I have my doubts (no punt intended for LEDs users). To be fair, there are LED users that has gotten very nice planted tanks. Again here is a personal preference.

The choice is yours to decide....

[David]

Just to add on.....

The height of your tank that you decide to get has a bearing to this matter of intensity. For example, if you want a 30cm suspension height from the waterline and your tank is 60cm in depth a 150 watt MH or a 6x39 watt of T5 may be considered (Please do remember that the light of the tank is not in the discussion here). However if you want a 10 to 15cm suspension height from the waterline and your tank is 45cm in depth, then the MH is out and a 4x39 or LED will be in the consideration.

[qngwn]

Personally i have not tried MH. I use the standard stands provided by the makers of the T5 set and the LED sets.

60X30X36 with 4 Tube T5HO
with the standard height of the stand, the light is around 10 to 15cm away from the waterline. ambient temperature around 28 deg, after 3 to 4 hours, the temperature usually hovers around 32 to 33 deg without any cooling equipment.
Light intensity at substrate level of the tank is acceptable, able to grow most plants.

36X20X23 with Green Element EVO12 Clip (6 X 3W LEDs)
with my green element 3W/bulb LEDs, temperature increase is slightly lesser, around 31 to 32 after around 4 hours.
Light intensity at substrate level of the tank is quite strong.

60X30X36 with 2X Up Aqua Z Series 2ft LED (~40W)
Not much noticable increase in water temperature, around 30 after around 4 hours.
Light intensity at substrate level of the tank is acceptable, able to grow most plants.

The above are just my experiences and intensity is subjective. I prefer a well lit tank with sufficient light reaching substrate level.
Do note the height of the tank has a huge effect on the intensity of the light reaching substrate level.

[Shadow]

I measured PAR of T5, MH and LED (about 15cm above water)
4x39W OSRAM 8000K T5HO
Top 142 umol/m2/s
Bottom 65 umol/m2/s (45cm deep)

150W ADA MH light (hang about 45m above water)
Top 167 umol/m2/s
Bottom 55 umol/m2/s (60cm deep)

50W LED generic brand (hang about 30cm above water)
Top 160 umol/m2/s
Bottom 38 umol/m2/s (90cm deep)

As you can see T5HO and MH is pretty much the same in term of watt and PAR, I ignore the fact that MH was hang much higher. LED on the other hand is the best among the three. With only 50W, third of the power, it is only slightly lower PAR than 150W MH.

All of the above measured using Seneye Reef PAR meter. PAR = Photosynthetically Active Radiation basically measuring the light used for photosynthesis. Unlike lux meter which measure everything, PAR meter only measure the photosynthesis spectrum.

[AQMS]

Im camping here...

[David]

Hi Shadow,

I cannot quite agree with your measurement due to the following reasons that in any experiment all perimeters must be held in constant

1. The suspension must be of the same height for all three.

2. The depth of the tank must be of the same height for all three.

3. The CRI (Kelvin) rating must be as close as possible (I think the T5s is rather low at 8000K and if I am not wrong there is T5s with rathing of 8500 or 8600).

4. All bulbs must be brand new from the start and possibly from the same bulb manufacturer.

I will buy the wattage matter that the electrical consumption for the MH and T5s will be greater than the LED though.

However duration should be measured of the same perimeters after one year of usage.

This is just my thoughts and an interesting point to share views Shadow....interesting test results though.

[qngwn]

Time to set up a aquarium lights research lab! an excuse to have more tanks!

[Shadow]

Good point. Let me share the reason behind the setup configuration.

1. The height was selected as how we normally use it. For example, just for measurement sake I hang MH light 15cm above the water. Sure I will get very high PAR but this is not practical because you cannot hand MH light 15cm above water without boiling the water surface. It is not apple to apple comparison but it is how we going to use it and at the end of the day that will be the most important.

2. Just look at the surface, ignore the bottom, because it really depend on the scape. Tall plant will block the light and reduce the PAR considerably. For example it may have 50 umol/m2/s initially but after plant grow it may drop to 30 umol/m2/s and carpet plant start to grow upward.

3. Its about what you can get readily and easily available from open market. That is why I mention the brand of the bulb. Different brand will certainly give different result, and there are hundreds of brand out there. By the way ADA light bulb is also 8000K. The LED is 7000K. I personally don't care about CRI, CRI is what human see not what plant see. You can get different spectrum combination and yet still have 8000K on the CRI diagram.

4. Yes all the light measured was new (LED and T5HO) or at least less than one month old (ADA bulb).

[felix_fx2]

borrow sense eye test on our setup and post here...

Sent from my GT-N7105

[David]

You have a point regarding practical usage. However, temperature is a variant that needs to be measured based on the consistency on height. Based on a standard magnetic ballast of an MH, agreed, the water surface will sharply increase and based on the readings, the user has to make certain decision to either increase height or add a chiller. In the market right now, there are MH with electronic ballast and the light unit is separated from the ballast unit thus reducing heat.

I agree with that light intensity to reach the bottom is critical. Which is why currently I suspend my MH lights at 20cm above waterline. Because the MH gives enough intensity that even when my background plant covers some part of the surface, the plants below the cover still gets enough light to grow well. Then again, I power a chiller to keep my temperature down.

CRI is important to a certain extend especially for PL, FL or the T5s. The intensity of a 10K Kelvin (used for reefers) is definitely more than a 4K Kelvin (used for fish only tank). While the wattage is the same tube for tube, but the glass used to create these bulbs varies. The quality and type of relectors used for T5s is also important of which I have left out of the equation for now.

So in retrospect, a good way to do this is to measure temperature and intensity with all 3 types at interval height levels. But then again to actually do this experiment is not going to be easy as we are all hobbyists and do not have the resources to do them or a real need to.

On a practical note, your reading is appreciated as at least there is a indication to how much intensity is going right to the bottom of the tank.....

[Shadow]

Best way is to get PAR meter and measure it your self because too many variable . The T5 light set that I used is modify to have individual reflector, so the original set probably lower . The LED is with 120 degree beam angle, PAR will be higher if I modify with 60 degree lens, another variable .

[David]

I think we left the thread originator, Mkt more confused than he originally started with.....

[Shadow]

Yeah he just open can of worms

[felix_fx2]

end up he will buy LED.... too many information... cannot digest...

[Urban Aquaria]

I guess most people nowadays end up buying LED lightsets, mainly because the prices are becoming competitive and many have already been using them successfully for planted and aquascaped tanks.

Most of the popular LFS are now stocking more and more choices of LED lights too, so its easier to find the right ones suitable for specific tank setups.

[David]

For smaller planted tanks that does not exceed 45cm in depth perhaps. Any deeper, I have my doubts.

From personal experience with LED downlights for my home was the determining factor. Originally when it was used for my kitchen in the beginning it was all well and good. 7 months in, it has definitely gone dimmer. There happened to be a power out in my estate and when the electricity came back on, 4 light set blew. Called the electrician and according to him, while LEDs consume less electricity, they are more prone to surges.

Went to the light shop to get replacement bulbs....guess what.....there isn't any. The only way is to replace with new light set.....

Perhaps it different with aquaria lights....those using LEDs.....try asking about replacement bulbs....to what I know, even if one of the electrode thingy goes out of twenty, the whole thing goes. I may be wrong though.

I am not saying that LEDs are not good....its just my opinion that perhaps in afew more years as technology advances...it gets better.

[David]

PS:.....and if I have to get an LED Set...it will definitely be this one (ALL BECAUSE IT LOOKS VERY GOOD...HAHAHAHA!!!)...I think there is a 120w and a 160w at 8K Kelvin for planted tank?







Suspended hardware kit for me FOR SURE.....

[felix_fx2]

@david, actually LED development quite fast since 3 years ago when i started planted. Not long from now will have one that would outshine MH, i am very sure of that.