[Incessant glass surfing lambchop rasboras (espei)]

To remove reflections make it very bright outside the tank, and very dark inside the tank.
Putting something up on the outside of the glass will make reflections worse, having a bright aquarium light shining inside the tank will make reflections worse. You need it dark inside the tank and bright outside the tank to remove the inner reflection from the glass surfaces inside the tank.

[What to use to seal decor.]

Looks like it is plastic, the warning about blue (UV) light is only bad for plastic. So it shouldn't need to be sealed, just rinsed well and put in the tank.

For plaster, clay or concrete things I recommend the epoxy resin used for fiberglass, it has a fairly thin consistency and is easy to just brush on.

[Adding Additional Air Valves to Air Loop]

I would leave the air pump running to help blow the chips out from drilling into the pipes.

[Shellies and Swordtails?]

Thinking of getting some Neolamprologus gracilis and putting them in a 75 gallon, letting the surface get covered by red root floaters and maybe have a few anubias on the rocks. Looking for a fish for the middle and top water levels, would red swordtails work with water this hard? I kept swordtails when I was a kid 50 years ago, and want to keep them again, but had fairly soft water back then and I'm not sure if swordtails can take the very hard water the shellies need.

[Whole house water filter]

Check the water hardness going into and out of the sediment filter. Is the filter medium crushed limestone or aragonite etc?
Changing the PH to 8.4 sounds like the water coming out is full of calcium carbonate.

[How Far Is Your LFS?]

Saltwater only store about 5 minutes away, nearest big box pet store about 10 minutes away, 30-45 minutes driving to LFS that have freshwater fish but there are three at that distance.

[Bucket Strainers - 4/25/2021 Live Stream]

Bucket Strainer on Amazon. Is available with different sizes of mesh, 55, 100, 200, 400 & 600 micron strainer

Also Stackable Strainer available in many different mesh sizes, from 1/2 inch down to 1/100 inch mesh.