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Confused about watts

1281 Views 6 Replies 3 Participants Last post by  Revernance
Right now I have a home depot shop light that is 48 inches long over a 29 gallon with a total of 80 watts. So I'm basically getting way less than 2 WPG (around 1.7 maybe considering the light is long)
Anyway, I wanted to add this to the back of the tank::partyman:

This new light is 36 watts total.
Does this mean that my new watts is: 36+ 80=116 watts total? :confused:

Right now I don't have enough money for AHS supply. Plus if i buy a new system, I would have to throw my existing light away. ($45!)
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The shop light is 48" long but the tank is only 30" long so you're getting roughly 63% of the 80 watts which is about 50w. So 50w from the old light + 36w from the new would be 86w total or 2.97 wpg. This is what? med-high to high light provided the reflectors are good. At least that's my best guess. :)
Thank you Cs_gardener.

Is there a better light for me to get, or should the coralife I mentioned above be best for my situation?
What is it that you're trying to grow? I have a 65w Satellite fixture over my 29 and I'm able to grow most things that I want. Foreground plants are a bit tricky for me though, so if you're set on getting a nice low-growing foreground you'll want a bit more light than I have.

I don't think there is a best light, though I wish there was because then there wouldn't be so much confusion. I have no experience with the light you linked to. Much depends on the reflector and I can't tell anything about the type of reflector that light has. I think the shop light you currently have is designed to spread light out rather than direct it down so you may be losing more light than I figured earlier.

Many people have been very happy with the AH Supply kits and rave about how much more light they get into the tank than with a fixture like my Satellite (those reflectors again). If you did save up and go that route, you could always keep the 4' light for a couple of smaller tanks that you'll undoubtedly be getting sometime in the future (ya' know - the must have shrimp tank, grow out tank, breeding tank, started as a quarantine tank but then ended up looking too nice tank, etc). :)
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I'm trying to grow medium light plants.

well that Coralife I'm looking at is a T-5, so I should get 1.2 WPG.

I read this post

and seems like 1.2 WPG of T-5 is really sufficient because I'm not ready for pressurized Co2 yet, just DIY co2.
Also, I'm trying to stay away from fertilizing because I'm only home once a week.
I need a light so that I can use DIY co2, and no dosing. :)
Light options now:


You probably have less than 29 gals of water in your tank even thou it is a 29 gallon size. Most tanks take the outside dimensions to come up with the tank size. After putting in substrate, rocks, plants, etc. you probably have more like 25 to 26 gals and then you need to subtract the amount of water in the substrate to come up with 'open' water space - the amount of water actually getting illuminated before you calc you wpg. It will bring the actual value up a bit.

Also, cs_gardener is right on.
Thank you Newt and cs_gardener.

I think i'm going to go with the 65 watt coralife. unless someone or something changes my mind )
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