Why do we not use submerged lights in our tanks?

Warning: DO not do this at home - I have no clue what the real risks are.

Some background:
On one of the other forums the guys are chatting about lighting and reflectors and building mathematical models to calculate PAR and such. I noticed that we loosed a bit of light in the math due to the light needing to penetrate the water and that it gets bounced of the waters surface.

So I have tried an experiment in my 4ft tank. It started by removing all the lights from the hood and adding a Juwel reflector with one 30watt. The I removed the hood and had only the tube and reflector resting on the 4ft middle brace. Happy with the continued improvement I then moved the reflector and the light to under the cross brace. This left only a few mm between the light and the water surface. The next step was to add enough water so that 40% of the tube is in the water - yes so are 2 of the 4 power pins. I was amazed to see the visible improvement in light on the substrate. True I now had a beam of light that originated in the water and that means the light slice does not light the full water column but it is a nice affect and seems more efficient at lighting the substrate. On the upside now the tubes heat keeps the tank warm - less load on the heater.

On the negative side:
This could be risky - but from a shock point we are talking 400 Volts at a max of .16 Ampere - so maybe sock risk is low.
Tube could burst - mercury (think it is mercury) and other nastiest in the water.

Question:
What am I missing .. why do we not have tubes and reflectors in the water - why do we keep them above the water?

BTW I get better substrate illumination now than what I did with the 30W + 4 x 18W tubes in a white painted hood.

Thanks Ferdie

 

Could you not manage to encase it in some plastic tubing and seal that, so that no actual electrical components are in contact with the water, and it's safe if it bursts. Cool Idea

 

I spotted this a while back in a shop ,I have never ever seen submerged lighting in a shop, except for this one shop ,if I remember correct the unit itself can be submerged thus if something goes wrong the bulb won't actually be in the tank ,ie the tube is encased ....I think the contributing factor as to why we don't use it is because of price ,it was damn expensive and secondly it would be hard to sell a very expensive kit that can work under water to newbies...they just won't sell ....f fish maybe you Can start the revolution? Ill head to the shop today and really scope those submerged lighting units out .

Cheers

 

Just to be clear - this is a normal T8 tube not one of those fancy boyu lights that cost an arm and a leg. One could probably silicone the end caps and add some around the glass the meets the electrode base. I wonder what the algae build-up would be on the light ... will keep an eye on that.

Later Ferdie

 

You do get units that are submersible but they are pricey like brads said. Looked like a light in a test tube.

 

Obviously the point f-fish is trying to achieve is the least amount of lost light due to the light trying to break the surface. This makes an interesting experiment Ferdie... to see if the growth justifies the lamp being submerged. I thing that with globes sitting in fittings ("like a test tube") you will get a similar effect to if the light was above... because the light will still need to "penetrate" the glass of the housing. It has already been shown in articles all over the web too that light going through glass looses a lot of the photosynthetic spectrum.

My only question is this: With the light being out of the water, when we are looking at our tank, we don't see the tubes. This is what we want... to see as little of the equipment as possible. Doesn't having the tube in the water defeat this purpose?

 

zoom .. "Doesn't having the tube in the water defeat this purpose" depends - if your view is just the window through the front glass or the tank as a and the surrounding.

Below a picture as it is currently.


note that the white space above the tank use to be the black standard hood now I am only using the 30 mm water brim for gear and have all the space above the tank to start playing with emersed growth and maybe a second light for that.

Consider my lucky 13 tank ... If I can have a tube in the water for the water bound plants and lights above the top plant growth then I can cater for both worlds.



So ideally I would want to add a light source into the water - hide it with some moss, plants etc and have on above the tank for the other plants. At the moment I move this 4ft tube down to water and then most of the shelf plants need to bend heads to catch the light.

So the question still stands why do we not have lights directly in the tank? What am I missing here? Extra load on the ballast (current leak via the water or is this due to marine legacy - higher salt content could mean more conductivity than in our tropical tanks greater chance of shock or just good practice cause we have been taught water and electricity do not mix?)

Later Ferdie

 

Just a few comments because I think this is a valid question and also the suggestions that have been made also all sound scientifically correct.

Firstly, I can suggest that you investigate those waterproof endcap fittings for T8s to see if they may actually be waterproof below water, I don't actually see why not. However, I would not put them far under water because of the water pressure. You must also cover the aluminium sleeve as this will corrode and will leach aluminium into the water which you do not want. The pins on the lights contain copper and you also want to cover this as well. The endcaps would cover all of this nicely though.

Then I think that the main opposition to your idea would come from electrical regulations that view any electrical fitting that is near water as risky for electrical leaks and thereby short circuits and with a human risk of shocks. However, if the connection can be made waterproof reliably then there is no reason why you should not be able to use them in the way.

You must also remember one other very important thing and that is that the glass that flourescent tubes are made of is very thin and if you give it a bash with a sharp object it will break very easily.

Keep us updated, sounds like an interesting concept, although to me a flourescent tube would look very unnatural below the water in my aquarium.

Kind regards,

Dirk

 

My 2C.
I had an underwater light(tube) once,but it was encased in a type of clear plastic and it was a 12 Volt Tube.
Gave a very nice lighting effect in the tank.
Wish i could find some now.

 

Thanks Prof ... I'll look into a way to avoid water contact on the aluminium and copper - point taken that they are not good for the aquarium environment. Let me go and put my thinking cap on since this means I would need to make a non aluminium based reflector also.

Later Ferdie

 

could you not use some sort of silicone, aquarium silicone for example, to seal the end caps?

 

Windfire - that is the plan but I also need to replace the aluminium reflector with something else .. all in all it seems that I am going to get best light use from a fully submerged tube with a white plastic reflection strip still in the water but just below the surface. New thing that is concerning me is the growth of algae on the tube ... but time will tell.

Later Ferdie

 

Remember that silicone rubber adheres well to glass but does not bond properly to PVC from which what most light fittings are made of, so you have some conflict here. However, I have not checked but I actually think the O-rings give quite a good seal so I am not sure if silicon rubber adhesive is really necessary.

Kind regards,

Dirk

 

Underwater Light

Bought one for R125-00 yesteday ,blue or red available fully submersible 9w looks awesome

 

Might sound stupid but here goes. What if you build two enclosures, similar to gutter filter made of glass. One in the front other in back. 10mm below water surface. You lie your light in there. Isolated from tank so no leakage.reflectance off glass but none of water and could even fill enclosure with water without negative effect on fish or plants
Regards
Washief

 

Hi Fiberoptic alias Washief,

Normal glass absorbs a massive amount of light, so any glass enclosures will reduce the amount of light dramatically, perhaps as much as 60%, so the approach of light boxes is not going to work unfortunately. I can agree that it appears obvious that this should work, but unfortunately glass absorbs light and this therefore will not work.

Kind regards,

Dirk

 

thank you for explaining that:bigsmile:

 

Thought I'd give quick feedback on this little experiment started a few months ago.

So nothing blew and nothing died during this period in this tank - actually plants did very well. What I did have was BBA like never before - even had to purchase some cleaners to help.

Had a good look at the light this afternoon while doing a WC ... decided it was time to quit the experiment and get the tank back into shape. So the lamp is now mounted in the hood again. Lets see if the BBA dies down.

Some observations:

BBA love to grow on the light and the reflector - making it less affective over time.


Corrotion was a real problem - I am sure we had some electrolysis happening over time.


This would probably mean copper in the water column ....

What was more interesting was the florescent coating in the tube cracking all along the typical water line. The light was only 1/2 way submerged most of the time.



This was a brand new tube when the experiment was started and now it still works but I get the feeling the life span might have been shortened ... note the faded coating on the side that was submerged and the cracked coating below on the HOT side.




Conclusion - yes it works, but I am not sure it is worth it in the current form.

Would need to do a fully submerged tube that has its contacts sealed. Also need to rethink the reflector or need for one if it is fully submerged. Regular BBA cleaning would be a requirement. The crack patterns in the coating is probably the biggest concern not sure what would happen if the light was fully submerged.

Later Ferdie

 

Hi Ferdie,

I am sure that some electrolysis was going on....

I think that the fact that tube was only half submerged had something to do with the condition of the light. The above water portion would have got a lot hotter than that below the water and at the water level the tube would have been subjected to different expansion due to the heat differences which I would firstly suspect for the tube degeration. If you wanted to repeat the experiment, I would recommend sealing the tube ends and submerging the tube fully.

Kind regards,

Dirk

 

100% Going to leave the tube in the hood for a while to see if the BBA dies down then I will do the fully submerged test.

Later Ferdie