Optically clear silicone?

[Starganderfish]

Can anyone advise on some genuinely clear silicone sealant that's Aquarium safe? Most sealant marketed as "Clear" is milky translucent at best.
Looking to make a submersible fuge light using a waterproof LED strip, in a 3D printed holder. Think of a long "U" shaped channel, with the strip embedded. The 3D printed part will be coated in and out with a thick waterproof sealant to prevent any water seeping into the layers lines. The LED strip goes in the channel and the channel is filled with a thick layer of clear silicone. Between the water-proof sealant, the silicone and the LED Strip itself being waterproof, along with care that the wiring and solder joints are properly sealed and out of the tank, it should be fine to stay submerged in the fuge.
Basically a DIY version of the Tunze ECO-CHic fuge light, built smaller for a PICO reef.

I have one of the official Tunze ones for my 20 Gal, but it;s much too large to comfortably fit in a 4 gal Pico. It basically uses teh same theory - the LED's are emedded in a soft, clear silicone

I've previously assembled and built a 3D printed fuge light for another PICO tank which has worked well, but it's not submersed. All the seams and joints are selaed with silicone to keep the water out but its by no means waterproof.

For the next tank, the fuge will be in a small AIO chamber in the tank and I find the light in the water with the Chaeto helps a lot.
If I can't get the silicone to work, the next idea would be use clear epoxy resin to fill the channel, because once cured thats completely inert and aquarium safe.
I prefer something with a bit of flex and give though and Epoxy has a tendedncy to yellow over time.
Current front runners are "Loctite Clear Silicone Waterproof Sealant" or "CRL Water Clear Silicone Sealant". I'm not sure how clear the Loctite is and while the CRL is stated to be perfectly clear, I'm not 100% on its durability in an aquarium environment.

Any thoughts or suggestions?

 

[xcountryx]

The loctite clear is realy nice. Ive used it many times and is pretty close to being as clear as the water. As long as it's not gooped on heavy

 

[Starganderfish]

The loctite clear is realy nice. Ive used it many times and is pretty close to being as clear as the water. As long as it's not gooped on heavy

Cool I might pick up and run some tests. I need it to be relatively thick to properly encase the LED strip so will see how that goes.
thanks

 

[AdamD76]

How about epoxy resin?
example

 

[Starganderfish]

How about epoxy resin?
example

Yeah, that's my alternate thought. I do know that resin has a tendency to yellow under UV, and given the spectrum emitted by reef lighting and the mix of red and blue lights in a fuge light, I'd worry about it yellowing over time. The resin you linked is UV resistant so that might help.
It would probably be more durable and less likely to split or leak - you could skip the 3d printed part, make a simple rectangular mould using cardboard and basically create a solid block of clear resin with a strip light embedded in it. Even embed a couple of those small 20mm suction cups, or maybe some powerful little magnets, into the back of the resin as it's curing so you have a permanent mounting solution.
Tossing up now between the silicone in 3d Printed mould, the resin solid block of resin or the test-tube idea from that other thread... I might try multiple and see what works!!

 

[Starganderfish]

Quick update is anyone is interested - I abandoned the idea of silicone to cover the lights and used the test tube idea. It was super easy, barely an inconvenience.
3D printed a holder for the LED strip to go inside the tube, glued the strip on the holder and inserted it into a 200mm test tube. Ran the wires out through the test tubes rubber cap. I sealed up both ends of the strip with silicone (its otherwise a waterproof strip with rubber covering all the bulbs) squeezed about 5mm of silicone into the tube between the holder and the rubber cap, and sealed off the wires and the top of the cap as well. The wires were coated in a thick layer of heat shrink wrap and all seams and potential leak points sealed with more silicone.
It's been running for about a week now off a smart timer and seems to be doing nicely - no sign of any leaks and algae is growing, albeit slowly (its a small tank). The lights aren't as well-blended as my Tunze ecochic, being distinct red and blue bulbs, and being shorter its a bit less bright, but it definitely works and was easy to build.
I'm calling this a success.

 

[AdamD76]

Very nice clean look. A+

 

[SteveMM62Reef]

Set the tube with the opening down, so any micro bubbles will travel upward. The longer it’s in this position the less micro bubbles. BTW, the company that replaced our windshields at work, had a specialized rack for holding silicone glues. It‘s purpose was to eliminate bubbles in the silicone, also they had different thicknesses of silicone, some was close to pourable.

 

[TheHunterYall]

Set the tube with the opening down, so any micro bubbles will travel upward. The longer it’s in this position the less micro bubbles. BTW, the company that replaced our windshields at work, had a specialized rack for holding silicone glues. It‘s purpose was to eliminate bubbles in the silicone, also they had different thicknesses of silicone, some was close to pourable.

Yes, I was going to suggest thinning it with something reef safe and experimenting with that.

 

[SteveMM62Reef]

Did a little research, this is the Flowable Silicone. Don‘t know if it is Reef Safe.

Permatex 81730 Flowable Silicone Windshield and Glass Sealer, 1.5 oz.​

 

[jkcoral]

Quick update is anyone is interested - I abandoned the idea of silicone to cover the lights and used the test tube idea. It was super easy, barely an inconvenience.
3D printed a holder for the LED strip to go inside the tube, glued the strip on the holder and inserted it into a 200mm test tube. Ran the wires out through the test tubes rubber cap. I sealed up both ends of the strip with silicone (its otherwise a waterproof strip with rubber covering all the bulbs) squeezed about 5mm of silicone into the tube between the holder and the rubber cap, and sealed off the wires and the top of the cap as well. The wires were coated in a thick layer of heat shrink wrap and all seams and potential leak points sealed with more silicone.
It's been running for about a week now off a smart timer and seems to be doing nicely - no sign of any leaks and algae is growing, albeit slowly (its a small tank). The lights aren't as well-blended as my Tunze ecochic, being distinct red and blue bulbs, and being shorter its a bit less bright, but it definitely works and was easy to build.
I'm calling this a success.

This looks like an awesome solution. I’ve been thinking about how to make my own like this for my IM 30g AIO. Using a test tube never crossed my mind!

Are you using a specific type/brand of LED strip? Would you mind sharing? Amazon returns a billion results for LED strips and it gets dizzying haha.

Also, is there any reason that some aquarium silicone wouldn’t work for sealing the stopper on the tube? I’m just curious and was wondering if maybe the materials (rubber stopper/glass) being bonded would make aquarium silicone risky.