I think silicone seams would be alright. The advantage is you can take it apart and take it with you easier if or when you move.Yes the tank is 316 stainless steel and is 6mm thick plate. I have seen those for sale that you attached but they have a few downsides. Theres alot of silicone seams to trust compared to welded joints and the glass is toughened glass which i dont have much confidence in and dont seem strong enough to withstand the corruscons or arapaima. The size tank shown is approx 2metres x 2metres? Not big enough and there limited on height (max 2 foot i think i remember) and if you brought enough lengths to extend to anything near same as what ive got the cost is huge. With mine theres no chance of leaks other than the acrylic to frame as there welded and we have tanks at workthat are half the thickness and have been leak free for 40years plus.
Their tanks have different sizes and depths: click on pricing / order form http://www.atlanticagardens.com/instantpond
Yea, the glass could be the weak point if a large fish slams against it. My guys in 4500 gal are still relatively little but hit the walls very hard every now and then. If I happen to be near the tank, I am stunned by the force of the impact and the sound.