yes... the rim is there for a reason, because these tank usually have thinner glass than rimless tanks. and with a 20 gallon long tank, you're looking at almost 30 inches in length on the long side. you can expect some bowing of the glass.
i would not recommend it, but there will be others who will say they have had no issues. the choice is yours.
Well..May be just remove the front part of the rim then you only have to worry about the 2 front corner coming apart. The back rim would give the tank better support wit hall the wiring and hoses, etc....Good luck
Not sure I'd want 20 gallons of water on the floor.
I will tell you I had a 55g and the center brace broke. The tank had a huge visible bow in the glass and I literally RAN out and bought a new 72 before the thing let loose. That was a 55. But just sayin'.
well I'll tell ya, I had a couple different old tanks that I bought and set up and about a week later I was cleaning one of the 20 gallons (was a regular 20, not a long) and wiping off the top rim and it just... came off in my hand lol. I figured what the hey? It wasn't supporting anything in the first place, might as well leave it.
I don't know about the long tank if the extra 6" of length will have much of a more adverse effect or not. If you were handy enough you might be able to fashion a brace of your own for the center, as that's the most danger you'll find. The seams aren't likely to run into to much trouble on a tank that small.
not sure where you would go to get glass like that. I would suggest looking in the phone book. I would also suggest that you just get a new tank because the price on the tank is probably close to what it would cost to get replacement glass, then silicone to add the new glass. Plus it would be a pain to do all of that.