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Aqueon 15W 18" T8: light too low

This is a discussion on Aqueon 15W 18" T8: light too low within the Beginner Planted Aquarium forums, part of the Beginner Freshwater Aquarium category; --> Thanks a lot for the reference to the other thread. The plants have been in the tank since roughly since May or June, but ...

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Aqueon 15W 18" T8: light too low
Old 08-12-2012, 07:54 AM   #11
 
Thanks a lot for the reference to the other thread. The plants have been in the tank since roughly since May or June, but I know what you mean about "settling in." They were doing very well until about a month ago. Except for the Wisteria which grew noticeably slower than the others. I also lost a Pygmy Chain Sword that was in full light.
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Old 08-12-2012, 10:01 AM   #12
 
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Originally Posted by Mikaila31 View Post
How exactly are the plants dying? What are the symptoms?

1.5wpg is certainly enough light for plants in a 10 gallon. I would say you may have a nutrient deficiency. Thats usually what a sudden halt in growth points to when not much has changed.
Here are some pics of the plants in my tank, such as they are:
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Last edited by equatics; 08-12-2012 at 10:04 AM..
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Old 08-12-2012, 01:08 PM   #13
 
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I think it is the light but likely nutrients too. The "new" growth on the Wisteria for instance is the wider leaf form, which is one way the plant reacts in an attempt to get more light. I've had exactly the same under dual T8 tubes. This plant needs good light and nutrients.

If the light up to now was that single Aqueon tube, then it was not sufficient. Mikaila is correct on the 1.5 wpg being adequate, but not with poor light to start with. A single tube full spectrum/cool white would be sufficient for most of these plants, though the Wisteria and Cabomba may still struggle.

On the Flourish, I would dose it twice weekly. You mentioned a figure previously, but if this were me I would add about 1/2 teaspoon twice weekly. I do this in my 10g and I have Cabomba which is fairly new (3 weeks) and so far it is growing slow but healthy. I haven't tried Cabomba in many years, and not since I changed over to my more recent lighting/nutrient program so I 'm testing it out.

Byron.
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Old 08-12-2012, 01:27 PM   #14
 
Thanks for the help Byron. I'll start dosing as you suggest this week. Hope to see progress soon.
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Old 08-12-2012, 05:03 PM   #15
 
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If the plant bulbs reduce green light without increasing the red/blue light then yes, the light output would be less. But if the difference in spectral output is relative (which I am assuming), the overall light output will be largely the same quantity just different qualitatively. This cannot be determined just by looking at the light, for the reason I have explained before.

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I know after years of using the tubes that plants will grow much stronger under full spectrum lighting as opposed to these so-called plant or aquarium tubes, when they are in the same size/wattage
On this point, why do you assume this was/is due to more light? Maybe the better growth was due to 'better' light. See: http://jxb.oxfordjournals.org/content/61/5/1267.long, and this that I had linked to previously: http://pcp.oxfordjournals.org/content/50/4/684.full for a couple of explanations as to why it may be the latter rather than the former.
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Old 08-12-2012, 06:31 PM   #16
 
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Quote:
Originally Posted by Quantum View Post
If the plant bulbs reduce green light without increasing the red/blue light then yes, the light output would be less. But if the difference in spectral output is relative (which I am assuming), the overall light output will be largely the same quantity just different qualitatively. This cannot be determined just by looking at the light, for the reason I have explained before.

On this point, why do you assume this was/is due to more light? Maybe the better growth was due to 'better' light. See: http://jxb.oxfordjournals.org/content/61/5/1267.long, and this that I had linked to previously: http://pcp.oxfordjournals.org/content/50/4/684.full for a couple of explanations as to why it may be the latter rather than the former.
I don't fully fathom the technical aspects, but I do know that aquarium plants grow better with full spectrum/cool white light, high in red, blue and green. This spectrum is "brighter" and I've no idea what this may mean except that it is more capable of driving photosynthesis.

I know you disagree on lumens, but several plant sources still say this is significant. And the full spectrum may have 400 lumens compared to the aqua-type tubes 200. This would seem to correspond to the intensity/brightness, no matter how it may actually relate.

The above-linked studies both use terrestrial plants. I remember the cucumbers, this came up in one of my plant groups a while back, and I cannot remember who it was that pointed this out, and went on about water reducing the intensity of light more than air. The level of TDS in water also impacts this.

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Old 08-12-2012, 07:43 PM   #17
 
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Quote:
Originally Posted by Byron View Post
I do know that aquarium plants grow better with full spectrum/cool white light, high in red, blue and green.
On this we agree. The spectrum that most closely matches natural sunlight seems to be best for plant growth, which makes sense logically as that is the environment in which they evolved. The studies linked, while not perfectly applicable, appear to support this.
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Old 08-12-2012, 11:53 PM   #18
 
I have two 20W T12s over my 10g now. They are from 1990. The tube in the Aqueon hood was a 15W T8. The more I find out about the two 20W the more worried I am getting about a massive algae bloom. Do I really have to worry about this?

This is a hardware store double strip light. Maybe back then the fixtures weren't as efficient as they are now.
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Old 08-13-2012, 07:23 AM   #19
 
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T8s are more efficient, so even though the T12s are higher watts, the light output will be about the same per unit length. But, keep in mind that it is the ballast in the fixture that determines wattage, not the tube itself. So for instance, a T12 bulb in a fixture meant for T8s will be underdriven since they need more current than the T8 ballast provides. As a result it will produce less light than it would with the correct ballast. I think it is recommended not to use T8s in T12 fixtures without also changing to a T8 ballast, I assume this is because the T12 ballast would deliver higher current than the T8 bulb was designed for.

Regardless, two of either of these over a 10 gal is somewhat high light. I tried a dual 18" T8 over a 20 gal (16" tall) and had algae issues. This was without CO2 and using only comprehensive fert. Whether or not you get algae depends on your specific set-up, i.e. plant species and nutrients, etc.
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Old 08-13-2012, 09:57 AM   #20
 
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Agree. And another point, when you say from 1990, do you mean the tubes have been in use since then (in use for at least say 12 months of 8 hour days)? They will be next to useless now. Tubes weaken in intensity as they burn, and the T12 were bad for this. Karen Randall used to suggest replacement at 6-month intervals for T12, whereas most agree T8 will last at least a year and perhaps longer when burnt daily for normal periods (8-12 hours).

When these tubes weaken over time, the plants cannot get sufficient light and photosynthesis slows, and may even cease. Algae takes advantage. I have found more than once that if brush algae starts to increase, changing the tubes stops it. This occurs if I go past 12 months. It's all about that crucial balance.
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