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What lighting changes will have a positive impact on the reduction of algae?

  • Reduce lighting period

    Votes: 119 32.1%
  • Reduce lighting intensity

    Votes: 45 12.1%
  • Reduce lighting period and intensity

    Votes: 83 22.4%
  • Program a "noon" burst of light (ie 3hrs 1.5wpg, 4hrs 3wpg, 3hrs 1.5wpg)

    Votes: 36 9.7%
  • Program a lights off "siesta" (ie lights on 5hrs, off for 5hrs, on for 5hrs)

    Votes: 33 8.9%
  • Change the spectrum/color temperature of lights

    Votes: 24 6.5%
  • I don't know: I never have algae! ;-)

    Votes: 31 8.4%
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3,819 Posts
I've said this before, but I grew some of my nicest Rotala macrandra and Pogostemon stellatus with 136 of T-8 (96w, 9325K) and T-12 (40w, 5500K? Nutrigrow) lighting. I did have pressurized CO2 which was a big help. Algae was practically non existent and P. stellatus rarely if ever stunted. The plants grew much slower with that amount of light, but so did the algae.

Why is it that such high light levels are recommended and do we really need it for most plants?

3,819 Posts
I have read through this thread again and it does seem that reducing the lighting period (a "noon burst" may also be considered a light reduction depending on the application) may be the best effort to reducing algae. A lot of folks with high light tanks (myself included), seem to have some issues with algae in their tanks.

I think the majority of issues are CO2 related since fertilizing has been covered pretty much by the EI and PPS methods so fertilizer deficiencies should not be much an issue any longer. Some folks just just can't seem to get enough CO2 into their tanks regardless of their methods and reducing the light intensity/duration will help with CO2 levels.

I have combatted both Green Dust and Diatoms successfully by reducing my photoperiod and intensity of lights. I think the one things we may have overlooked (or not mentioned) thus far in this discussion is determining and or applying the Watts Per Gallon rule.

Wasn't the WPG rule created a long time ago when T-12 lamps were our only source of lighting for planted tanks other than incandescent bulbs? T-8 lights have now replaced T-12 lamps in most commercial strip light fixtures today. T-8 lamps give us more intensity per watt when compared to T-12 lamps. How much do we decrease the original wpg rule for the greater intensity of T-8 lamps?

Compact Flourescent lights are a big step up from the T-8 lamps in intensity per watt yet people still use 3+ watts per gallon with these more intense sources of light. Do we need to decrease the WPG rule more to take this more intense light source into consideration? How much more intense are PC lamps..are they double the intensity of T-12 lamps?

I believe the linear T-5 lamps are an even greater increase in intensity over the compact flourescent lamps since they have less restrike and possibly even better reflectors. Should the WPG rule be decreased even more for linear T-5 lamps and if so, by how much?

One of the SWOAPE members, rwoehr, is growing a nice variety of plants in his 75g tank with 108 watts of T-5 lights. I don't think I would try to grow those plants with 120w of T-12 lighting over a 75g tank ;)

I realize the WPG rule was originally devised to make it easier on new hobbyists to select lighting for their tanks but again, it was created with the inefficient (by today's standards anyway) T-12 lamps.

We used to believe PO4 caused algae and a lot of folks now keep their tanks at 2ppm or better. It is now commonly believed that increasing PO4 levels actually reduces Green Spot algae. I really think when dealing with lighting and the WPG rule we need to revise it for todays higher intensity more efficient lamps. The fertilization methods have changed greatly since the WPG rule was developed why not revisit the WPG rule also?
1 - 2 of 2 Posts
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