# What lighting schedule?



## Marc1t (31 Mar 2015)

Hi there.
Not got much experience with planted aquariums, bit of a novis! I have. Just purchased a timer for my lights. I have a 2 foot cube planted quite heavily, no Co2 at the moment, with 2 T5 HO 24 W tubes, I've taken the reflectors off.
I'm not sure what timing schedule I should set, or how many hours I need to leave the lights on for optimal plant growth, while keeping the dreaded algae at bay. Can anyone suggest a schedule I could set? 
Many thanks 
Marc.


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## Rahms (31 Mar 2015)

People seem to find success by starting with lower light and a short photoperiod with a new scape, and ramping it up as the tank matures and the plants get settled. I'd go for 4 or 5 hours max to begin with, depending on your plants.

2x T5HO is a hell of a lot of light and you may need to reduce the intensity by using foil rings around the tubes, raising the light or, most simply, turning off one bulb (if possible).  However, if its a true cube (2ft deep) then the intensity at substrate level will be greatly reduced.  Handy chart I've seen ian_m post a few times:




 


its quite unlikely you'll provide too little light, though, so I'd play it safe and reduce it


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## alto (1 Apr 2015)

I don't know the source of the above diagram, but every time I see it I'm disturbed by the notion that if one has 2 x T5 lamps, the PAR is multiplied directly by the # of the lamps - this defies logic as the lamps will not be stacked in space but rather spread out over an increasing surface area dictated by - at the least - the physical dimensions of the lamps & fittings (there are also studies recommending optimum placement of the individual lamps & types of reflectors ... though manufacturers apparently seldom follow these guidelines) 

So as it finally disturbed me enough to find a decent PAR diagram ...
in this instance, a 6 X T5HO lamp fixture (this is from a reef oriented site, so light distance is 24 & 30 in but as both values occur in the above diagram, it allows a direct comparison)

Using the formula above, PAR x lamp # at 0.8 (for a 5-6 lamp fixture)
24 inches: 60 - 70PAR x 6 x 0.8 = 312 PAR (using the median 65) which is rather far off the actual values measured by Sanjay Joshi Ph.D. in the linked article
30 inches: 20 - 30PAR x 6 x 0.8 = 120 PAR (using the median 25) which at least is measured over a significant area of the light distribution ... except not many planted tanks run the lamp at this distance

(Sanjay Joshi Ph.D. has written several lighting technology articles for Advanced Aquarist)


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## Rahms (1 Apr 2015)

well its certainly an inaccurate assumption, but that inaccuracy is going to be most pronounced with 6 bulbs, and I don't think your plants are going to particularly care if the deathray above them is ~240 PAR or 312.  20% inaccuracy for a rule of thumb ain't bad, especially for the absolute worst case

Admittedly I also don't know the source though, just stole it from one of ian_m's posts!


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## ian_m (1 Apr 2015)

Rahms said:


> Admittedly I also don't know the source though, just stole it from one of ian_m's posts!


The source is plantedtank.net

http://www.plantedtank.net/forums/showthread.php?t=105774



alto said:


> don't know the source of the above diagram, but every time I see it I'm disturbed by the notion that if one has 2 x T5 lamps, the PAR is multiplied directly by the # of the lamps - this defies logic as the lamps will not be stacked in space but rather spread out over an increasing surface area dictated by - at the least - the physical dimensions of the lamps & fittings (there are also studies recommending optimum placement of the individual lamps & types of reflectors ... though manufacturers apparently seldom follow these guidelines)


Sorry you are wrong, please don't be disturbed, all patently obvious. As the tubes are generally closer together than the distance off the substrate, there is probably near 90% overlap of their outputs, therefore you need to just multiply the one tube PAR level by number of tubes. This is shown in practice as this graph is from actually measured light levels.

There are many repeated experiments like this, all giving same result, but none presented in such a useful handy graph.


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## Marc1t (1 Apr 2015)

Guys, keep it simple, I'm a novis at this & what's been said apart from Rhams comments & thank you, are complete gobbldegoop to me, I 'm sure you know what your talking about but hold the horses. I get it I could do with reducing the lighting but the graph doesn't make too much sence. The depth of my tank is really 2 feet, the graph would indicate that plant growth near the surface have too much light & the carpet plants will not have enough. I'm none the wiser.


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## Rahms (1 Apr 2015)

I think I'd just see how it goes with two tubes for 4 or 5 hours a day.  Two feet is really quite deep! There's no easy answer for me as I have no experience with a tank of these dimensions, so its just a case of picking something and seeing how your plants react...


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## alto (2 Apr 2015)

ian_m said:


> The source is plantedtank.net
> 
> http://www.plantedtank.net/forums/showthread.php?t=105774
> 
> Sorry you are wrong, please don't be disturbed, all patently obvious. As the tubes are generally closer together than the distance off the substrate, there is probably near 90% overlap of their outputs, therefore you need to just multiply the one tube PAR level by number of tubes. This is shown in practice as this graph is from actually measured light levels.



I'll completely disagree on the Me=Wrong bit, light distribution MUST be taken into account when considering those PAR readings - there is only a small light distribution area with those maximum PAR values. If the ATI fixture I found is the correct model, total width was ~ 9.5 inches - going back to that light distribution curve, once you're (your probe) no longer directly beneath the lamp, PAR values drop significantly, eg, at 12 inches (remember the last T5 lamp is located at ~ 9inches), PAR values are now in the 110 range - a far cry from that hypothetical 312 or even the measured 220 -   move out 6 inches from the outlier lamps, & PAR is 90 & so on ...

With a single lamp placed centrally over a tank, that maximum PAR range of 40-50 is unlikely to apply to "most" of the tank (assuming a 12in width) - unless you know something that is not written in this post - I didn't read the 50 pages  ... perhaps the values reported are already averaged over some light distribution area 
Also note that  40 - 50 PAR value was for T5HO with "good" reflectors: most fixtures on the market have more of what I'd consider "fair" reflectors.

My T5HO tubes are ~ 8inches apart, it's unlikely that the spectra show a 90% overlap (I don't have access to a decent sensor or data logger) but one can see the shadowed areas change as I physically move the light fixture across the width of the tank (60cm x 45 x 55cm, fixture holds lamps ~60cm above substrate).




ian_m said:


> There are many repeated experiments like this, all giving same result, but none presented in such a useful handy graph.


I'll stick with Sanjay Joshi & his light distribution curves (which agree with many other similar light distribution curves) - he also includes details on the materials & methods which show a thoughtful process & allow anyone to repeat the experiment.




Rahms said:


> well its certainly an inaccurate assumption, but that inaccuracy is going to be most pronounced with 6 bulbs, and I don't think your plants are going to particularly care if the deathray above them is ~240 PAR or 312.  20% inaccuracy for a rule of thumb ain't bad, especially for the absolute worst case



Not sure how you  determined the 20% ... 200-220 PAR (range measured) ~ 210 (median) / 312 (median) ~ 67% ... I'd consider  1/3 discrepancy to be notable.
If you utilize that pinpoint 220 - 240 PAR maximum which looks to have a distribution of maybe a 1inch circle .... then you're right, I have no comprehension 




Sorry Marc for making this so complex  


Marc1t said:


> The depth of my tank is really 2 feet, the graph would indicate that plant growth near the surface have too much light & the carpet plants will not have enough. I'm none the wiser.



This is true, as plants approach the lamp, PAR values increase significantly (you can often observe changes in leaf structure, color, speed of growth etc) - if you want good growth on carpet plants, then you need to consider what the PAR values are in that zone, OTOH plants are often more limited by CO2 availability in aquaria rather than light ...

You've not supplied much detail on your tank, it's heavily planted but how long has it been planted?
substrate?
fertilizers?
present light schedule?
no CO2 but what are other water values, eg, ,pH, KH, GH
types of plants?
water change schedule?
cycled filter?
algae crew?
fish?


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## ian_m (2 Apr 2015)

Marc1t said:


> Guys, keep it simple, I'm a novis at this


Well with your 24" gap and T5 no reflector (1/2 that with reflector) looking at the graph possibly 20PAR, 2 tubes 40PAR so in the lower end of medium light area.

Thus lower end of medium light, gas CO2 not required, EI fertilisation & weekly water changes not required. So tank will be "walking speed" and opposed to low light "crawling" or high light "running/dashing/jet packed"....

Thus you can probably start weekly (or more) liquid carbon dose, weekly (or more) fertilisation dose and water changes whenever (more water changes if tank not mature).

You have the super advantage that once tank is settled and it is under control  you can put reflectors on to increase light level and moved to a high light faster growing regime...


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## Another Phil (2 Apr 2015)

Hi Marc1t,



Marc1t said:


> The depth of my tank is really 2 feet, the graph would indicate that plant growth near the surface have too much light & the carpet plants will not have enough. I'm none the wiser.


 That's because of the way light spreads; at double the distance the light drops to 1/4, so plants at the top of the tank get more light. This causes problems as carpet plants need a lot of light and the plants we attach to wood higher up are generally low light plants from over-hung forest streams.
cheers phil


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## Rahms (4 Apr 2015)

alto said:


> Not sure how you  determined the 20% ... 200-220 PAR (range measured) ~ 210 (median) / 312 (median) ~ 67% ... I'd consider  1/3 discrepancy to be notable.
> If you utilize that pinpoint 220 - 240 PAR maximum which looks to have a distribution of maybe a 1inch circle .... then you're right, I have no comprehension



Well considering the original graph says "area directly below centre of bulb," it seems reasonable to pick that point when comparing, does it not? I don't think any of us have access to median values either, but nitpicking around the numbers is a waste of time .  Back to the point I actually made: the graph is obviously going to be at its absolute worst for 6 bulbs, and so "proving" that it is useless by showing 6 bulb data isn't particularly productive.  I don't even think I've ever even seen a 6 bulb setup on here? You can provide the most accurate 6 bulb data on earth, but its still likely less useful to OP than the original graph, since he only has 2....


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## Andy Thurston (7 Apr 2015)

ian_m said:


> The source is plantedtank.net
> 
> http://www.plantedtank.net/forums/showthread.php?t=105774
> 
> ...


and if you follow the link in that post you find par charts for some led lights too you just need to convert inches to millimetres

http://www.plantedtank.net/forums/showthread.php?t=184368


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