Here's one idea I have had, that doesn't require lowering the water level, so whatever sized tank you use, will have the full benefit of its full water volume, and would also eliminate any complications with filtering a half filled tank.
Using glass, acrylic, flexan, whatever type of clear material you would like that's most economical/easy to work with for yourself: build a clear canopy for the top of your aquarium, at least 1 to 1.5 x the height of your aquarium.
Installing one or two small computer fans on one of the sides would be the best option, as the air flow will keep the clear canopy from fogging up, allowing you to view the action.
Ideally, you want to used an aquarium with some type of center brace, so glass aquariums would work best for this case.
Next, you can rest a nice piece of manzanita wood on the center brace and secure it however you please, get creative, or just find a piece large enough that it won't move or fall into the tank, once it is sitting inside the 'canopy'.
Here's the fun part:
This setup would work best with a lid installed on the canopy so that you can feed gut loaded crickets by letting them crawl all over the manzanita branch, which will attract the attention of the archers. The lid will keep the crickets from getting out, and block the water from missed shots wetting your walls/ceiling, near by electronics, etc....
They will then spit at the food and given the 1 to 1.5x height of the canopy, (lights installed on top of the canopy) you will really get to see the archers' sharp shooting.
After a while, the water being spit by the archers will leave water stains on the inside of the canopy, so you will have to remove it for maintenance and cleaning, but when setup correctly, it would be a beautiful display.
