After over 4 years of being tankless, I'm finally getting another one built. Earlier this year, I picked up a NIB Nuvo 38 at a great price, gutted it & totally disassembled it.
Every last trace of old silicone was removed, which was a lot of work. Interestingly, I found that Magic Erasers work quite well for taking care of that extremely thin layer of silicone which remains after using a razor blade scraper.
The new rear wall is 1/2" PVC. I opted to use PVC because it's easy to work with. I've done my share of cutting holes in glass, but really didn't want the hassle, among other reasons.
I used ASI 500AQ silicone (a very high-modulus silicone specifically made for aquarium fabrication); I called ASI and talked with a product specialist, who assured me the the 500AQ silicone would adhere strongly to the PVC as long as the gloss on the PVC surface was removed with fine sandpaper. So, I sanded all of the applicable surfaces with 320 grit sandpaper before assembly. He said it will be about 85% as strong as an identical bond to glass of the same edge thickness. That sounded more than adequate to me, especially since the PVC is much thicker than the original glass rear.
I despise powerheads being visible in the tank, so there won't be any. Instead, the rear of the tank will have an external overflow and inlets for multiple returns from 2 return pumps.
It's been over 25 years since I fully assembled a glass tank, so I'm quite happy with the silicone job along the bottom edges.
The threaded holes you see in the back wall will be used for short fan-out nozzles. I might not use all of them - it will take some experimenting to find out what works best. Any holes I don't use will be plugged.
I mentioned TWO return pumps - they will both be Tunze SILENCE 1073.05 controllable pumps; they will be operated by my Apex in alternating/opposing up and down ramp manner - as one ramps up in speed, the other will ramp down, then they will reverse. So, this will create variable, alternating flow. The return distribution manifold which will be on the back of the tank will be split into two halves; each pump will feed water to one side. At least that's the plan... we'll see how it goes... it might work great, it might be a total bust.
I assembled it this past weekend, so the silicone will be cured enough for me to continue working on it this weekend, assembling the overflow and return distribution manifold which will be on the rear of the tank. Once all is tested and ready, I will cover the inside of the rear panel with black polyurethane pond foam.
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. I'll try again with a different brand. The foam I had used on my old 120 back wall worked great - it slumped a fair amount and gave a much nicer, less fake look. It was also denser. But it's no longer available. Anyone know of a black polyurethane foam that has relatively low expansion?
