Amount of Pearling a Good Metric for Light Efficacy?

[Ratfish]

I have a well-established but recently aquascaped 10 gallon tank that usually has 3 f17t8/865 tubes over it. I replaced one of them with a GE f20T12 plant and aquarium bulb and I noticed a lot less pearling. I switched back and it went back to normal. This is without anything else really changing.

Is it safe to say that since pearling is indicating the rapidity with which the plants are photosynthesizing, that the bulbs that cause the greatest amount of it are likely the best ones?

I'm also seeing rapid growth (mostly with the vals) but I think it would be much harder to gauge whether one bulb has them growing faster than another.

[DoctaQ]

pearling also has to do with flow and co2 and nutrient levels, which even in the same tank can vary from day to day, if you want to make it into a real experiment then you have to control the conditions

[Ratfish]

Well, given the fact that I am not currently adding fertilizer and always feed the same amount, I'm guessing that, if anything, the available nutrient levels went down during the same period. CO2 is DIY so I suppose that could have changed, but it's still a wacky coincidence.

I like the appearance of these bulbs more and the tank is doing well so I'm going to stick with them, but I was considering trying other bulbs in the near future and was wondering if this method would make logical sense.

[jpappy789]

I think, don't quote me on it, pearling has to do with the rate of Co2 use by your plants. They'll use the carbon and then O2 is released. Bascially, it corresponds to maximum plant growth.

[Yoemen]

actually it is more to do with the amount of dissolved gas present in the aquarium, not just CO2.

If you pump up the CO2 injection on an aquarium, the water will become saturated and you will have pearling with fake plants.

Course you will also have dead fish.

[DoctaQ]

well, co2 is something you can measure and so are some of the nutrient levels
you could try to control as many of the parameters as possible
higher light temps usually will get less algae, so look for bluer light i guess

[jpappy789]

well, co2 is something you can measure and so are some of the nutrient levels
you could try to control as many of the parameters as possible
higher light temps usually will get less algae, so look for bluer light i guess
How so?

Many people run bulbs aroun 6500-6700K (looks more yellow) without getting algae. Plants do benefit from light in the blue spectrum, as well as red, but a pure blue bulb is not going to work.

Sometimes, the opposite gets thrown around: that actinic lighting causes FW algae. Its yet to be proven as the sole culprit.

When it comes to algae, balance is key.

[DoctaQ]

i guess i mostly meant that 6700 will give you less than say 3300 or whatever incandescent or warm white is, i dont know how far it goes though, while comparing actinics is taking it pretty far, its not really a color temperature per se, its so monochromatic, generally, talking like 420nm? thats what they aim for anyways

[jpappy789]

I didnt quite understand what you meant, so yes actinic is an extreme example. Its more about whats useable for plants. Most consider 6500-10000K a good range.

[zzyzx85]

The reason why 6500-10000K bulbs work better than softer white bulbs with algae is because the bulbs let the plants better utilize the available nutrients in the water. This less nutrients for algae floating around in the water column.

[blackwolfXKAV]

I suppose one could use pearling as a metric if all other non-light related variables were relatively constant at appropriate levels.

Then again, I think there are easier ways to gauge plant health, like growth rate and coloration (the whole deal with reddish colors and iron ions for example).

If you wanted to really break down the light efficacy, i suppose you could plug in the intensity of the light, the area of the tank, and the turbidity into a couple of equations that would give you a qualitative result.

[jpappy789]

I believe the most accurate readings in terms of useable light for photosynthesis come from PAR meters...