Get a half gallon, they have like an inch wide mouth and its a good size for a tank. three olives is nice but most of the bottles are sanded. Skyy and absolute have nice half gallons that would work well too. cutting the top off would be cool, you could save the neck and get a light that fits inside to make it way cooler.
Feel like a fish out of water/A mouse in this rat race
Drowning in the tartar/Lonely like stars in the outerspace