Leak Locating and dismissal, and general advice

[Hitman962]

I am the proud owner of a 230 gallon aquarium with 1/2" plate glass and 2 holes drilled for bulkhead and plumbing. I have had a 55 gallon aquarium for many years but not for the past 12 years. At that time, I gave my aquarium away and dug a 3,000 gallon pond in my backyard. We thoroughly enjoyed our pond, the gold fish, koi, shubukin and all the other creatures the pond attracted including a blue heron, which tried to eat our fish, and a deer. Since we are in the middle of town, the deer was a mystery. We've also attracted a pair of ducks every Spring, a garter snake we've named Snicker, and hummingbirds which hover and pick off the gnats one by one after they've visited our hummingbird bush.
The 230 gallon aquarium I bought was sold to me so cheaply because it has a leak and the former owners didn't want to be bothered with finding and fixing it again. After comparing the price I paid with the prices wanted for the same size aquarium in town, I feel like a thief; but they agreed to the price and the deal was done. I have gone to websites that list methods for finding leaks in aquariums so I can try those after I build a stand. I see no reason to buy one when those I see on youtube.com that are handbuilt are all so beautiful. I have found a design that I know will support the ton of weight that will be placed upon it and I have a friend who is a carpenter and is willing to help with my build.
The reason I am writing to the group is to see if anyone has any suggestions on how the leak can be found. I plan to build my aquarium stand, place my 230 gallon aquarium on it outside, then fill it 25% and see if it leaks. Then the next day, fill it up halfway and again watch for leaks. The following day, 75%, then all the way. Finding the leak, even though I can see the water on this side or that, is still a problem. This aquarium has been sealed with black caulk of some kind. It doesn't look good, but the previous owners covered it with oak corner mounding. I can do the same I suppose but I prefer the clear caulking to this black stuff. The photo attached shows the moulding in front and the black stuff in the back corner.
Also, if anyone has any suggestions on adjusting to my new aquarium, which is 4 times larger than my 55 gallon, I'd appreciate it. I've never had an aquarium with holes drilled in the bottom. The Pleco in my 55 gallon tank was 18" long. I wonder how long he'd be if he was in my new aquarium? I plan to try and make a few plastic plants to see if they will look good. And I'm already on a rock hunt.
I haven't decided to go with fresh water or salt water yet but that's 2nd. First on my list of finding the leak. Please help. Hitman962

[Brookster123]

No photo, I'd just reseal the entire tank to be honest.. especially if it looks sloppy and is leaking? Chances are it was not done properly in the first place. 230 gallons may be a splash in the pond but it'd be a nightmare on the dining room floor.. as for the silicone required?? With that size tank you'd probably be in the market for something a bit stronger than GE I. pm mr. X, he's the guy for the big tank builds..

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[J.Mcpeak]

What he said except, if you are resealing the strength of the tank remains in the original build and you reline the internal area. Any safe silicone will do it. It's only a thin bead so a tube should do it.

Reseals are simple enough but time should be taken removing the silicone and cleaning before you reseal, it takes a while to remove the bits because they stick to the glass a damp tissue is good for getting them.

Siliconed surfaces must be dry so if it gets too wet with the cleaning allow it to dry fully, overnight is what I did.