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Transparent Light Cover (Looks like fresnel lens)

2K views 5 replies 3 participants last post by  Fat Guy 
#1 ·
My tank hood has built in light fixture. There is this transparent light cover just below the lights. This light cover looks like fresnel lens, should evenly distribute the light to entire tank (Hopefully) and to prevent water reaching the electronics.

Should I remove this plastic cover or leave it there. I have brown algae on both my Anubias Nana and Java Fern. Will this transparent light cover reduce light performance reaching the bottom?

My tank parameter is as follow:
48x18x18

Water depth
14 inch

Light
2x30w Azoo Plant Fluorescent Tube[/url]
 
#2 ·
That's interesting. I've never heard of a Fresnel Lens being used in aquarian before. Does the fixture also have a reflector? I think you're better off with leaving the lens in place, as it is helping to redirect light straight downwards into the tank. Your brown algae is usually due to an imbalance in nutrients. What are your NO3 and PO4 levels and what is your trace element dosing regimen?
Even if you did get your nutrient levels in perfect alignment, you have a very, very low light planted tank. Some algae is going to be inevitable with the slow growth rate of plants and subsequent slow uptake of nutrients. Since nutrients are consumed so slowly, it is hard to prevent algae from taking advantage of them.
Unless the two 30 watt lights aren't the only lights you have on your ~65gallon tank, you could definitely stand to upgrade your lighting a bit.
 
#3 ·
Since fluorescent tube are long, it doesnt look like the fresnel lens used in overhead projector (Circular). But the inner side of the cover is jagged straight from one end to the other(Total length of the cover). If look from the side, its like little pyramids or prism bending the light. Should this cover distribute the light evenly and reducing light density?

My No3 is around 0 - 10 ppm. I dont have a test kit for Po4.

Heard that brown algae will grow in newly setup tank. Yes mine is just 2 months old. Also read from some other source, it is also because the tank is poorly lit.

I am thinking of adding the 3rd tube, but the tank hood only takes 2. It is possible to do some DIY to add in the 3rd tube but that of course. The light cover has to go as it only have enough space to house 2 tube.
 
#4 ·
Well if the cover is actually a diffusor, then it will increase light intensity towards the bottom a bit if you remove the diffusor. I really wouldn't worry about the lens, though. The difference with or without it is only a few percent and you need well over 100% more light to get good plant growth.
Aside from the low light, you've got two other things working against you - the tank is new and as yet unsettled, and you do not know what your PO4 levels are. If they are above 1ppm, then your algae problem is going to continue to get a lot worse, and at a rapid rate. My first step would be to get a PO4 test kit and make sure your levels are between 0.5ppm and 1.0ppm.
Then I would start working on that DIY canopy with more lights!
 
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