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Glass lid and light

Jaap

Jaap

Member
Joined
30 Sep 2011
Messages
1,068
Location
Nicosia
Hello,

I have a TMC Aquabar 600 with a controller and week by week I have reached 100% intensity with very good growth and no algae. Now I have added a glass lid onto the tank and it gets alot of condensation on it.

How much will the clear 4mm glass lid and the condensation drops block my light? Will it be as if it was 80%?

Thanks!
 
Well I'm no expert but since I added one, my plants seem to be doing much better .. Less algae for sure .. This tells me that my light was too bright in the first place and the lid has dampened the Rays slightly... But by how much I couldn't tell you :)


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IMO I feel there is a 30% reduction from covers and condensation .I do plan on buying a meter so i can read par values.
Be assured that covers are bad for light penetration, just ask any reef keeper .
 
ok so I guess I need to lower the light fixture.....now its 55cm from the substrate....should i go to 50cm and then to 45cm and so forth? I mean a 5cm decrease is good or is it too much?
 
30% reduction seems a lot, I might be coming at this the wrong way but will a layer of condensation under a cover be about the same as topping up the water level by that much.
The light still needs to travel through just water.
Or am I missing something relating to light diffusion?
 
I think its the refraction that scatters the light.Think of the bubbles on the glass like a bunch of reflectors throwing the light sideways etc.
30% may be high but that note you always will have a hard water film on the glass because of the intensity lighting we use
 
Yes but with r
drodgers said:
IMO I feel there is a 30% reduction from covers and condensation. I do plan on buying a meter so i can read par values.
Be assured that covers are bad for light penetration, just ask any reef keeper .
Click to expand...

With reefs you get deposits of salts on the glass so definitely a no no. I soon learnt that one and always had an open top on my 6' reef. Also corals especially hard corals like sps are very light demanding. As I'm learning on this forum it appears that plants are not so light demanding as many have been led to believe. So I'm keeping my glass condensation lids for my aquagrow 600's to rest on. Plant growth is great so I'm happy. Saying that I do love these open top aquariums with the water right to the top with no braces etc. Looks fantastic but how do they keep their fish and shrimp in them ;)
 
Can anyone with a PAR meter inform us of the loss in light when using a glass lid?
 
I was wondering about this a while back and found some information on reef forums. If memory serves, they weren't overly concerned with loss as it was so little - under 1% (If kept clean!)… a quick dip into the salty forums will be your best bet for more detailed info.

they may of been talking about glass covers on lights not the tanks… it was a while back. Just disregard:crazy:
 
Last edited:
Jaap said:
Can anyone with a PAR meter inform us of the loss in light when using a glass lid?
Click to expand...

Would love to see the results of a accurate experiment.
Compare high iron glass (green) over clear low iron etc .
I have some lids I have that came with a second hand tank that have mineral etching so bad i bet they block half the light :)
 
Theres a reef thread somewhere that show this being measured. 30% sounds about right to me with clean glass. the condensation doesn't play too much of a part really its more dust and salt deposits and the fact that clear glass / acrylic isn't as clear as air.

The reef thread that measured it recorded over 50% losses but that was without cleaning the glass.
 
Before people start pumping photons, scared they have too little light, here's a photo with my tank:
15517450028_b39387c2ba_c.jpg

I'm using 2x18w T8s / 60l, no reflectors, 10cm above the surface and a plexi lid, most of the time covered in dust.
 
how do you get that all white background for the photo no see through tank back or sides
 
You could always use a piece of self cleaning glass for a glass lid , this should stop the condensation to a certain degree , as it will have a special coating in which water doesn't like to 'adhere' to , a bit like if you were to spray a surface with silicone spray .

Just a thought
 
Reference;popularfishkeeping.co.uk January-February 2014

Air versus light Living plants depend on the energy from specific wavelengths of light, in order to be able to photosynthesis and thus grow. Simply placing a light over an aquarium will not guarantee that your plants will thrive – it needs to be of the right type. Water itself has what is known as a V value or refractive index. Every transparent item has its own refractive index and it is this index that dictates just how light passes through the medium concerned. Air is denoted by an index
of just 1.00. This means that light travels through air very well indeed, and is not changed very much in terms of concentration or color aberration, meaning that its brightness and color are not affected. In contrast, the refractive index of water is around 1.33 and as such, the light itself entering here will be concentrated into a smaller area and it becomes more subject to both color aberration and color change. In this type of situation, many PAR readings that are taken are inaccurate. A reading from a PAR meter taken through air will always be higher than if the same lamp is directed through water. When checking on the stated PAR level for your aquarium therefore, you should be clear that the figure advertised has indeed been taken through water and not through the air. It is also worth pointing out that if salt is added to an aquarium, even to create a brackish rather than a marine set-up, the refractive index
increases marginally, and this will still be sufficient to impact on the light and its passage through the water. In terms of cold water or tropical aquariums where live plants are not included, or if low light species of plants are chosen, then the PAR output of a lighting product does not matter too much. Fish are not reliant upon solar energy in the same way as reptiles and birds, and therefore a lower power light fitting can be safely used, without any risk of harm to their health. This light source, however, should be of a sufficient quality to show the fish themselves off in the very best light, so to speak
 
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