This is going to be a matter of opinion really, but if this was my tank, I certainly would try my best NOT to put my existing fish in jeopardy and while many people report that Bala Sharks are hardy, I do not think they would be good candidates for cycling purposes (again, more my opinion and my experience)
I read recently that for very large tanks, adding pure, unscented, undyed ammonia is really the fastest way to go because you can skip the waitng between adding fish and feeding them until they create enough wastes to properly cycle the tank. Also, with ammonia, you can generate a large enough bacterial colony rather than the size of the colony being so dependant on how many fish you have in the tank as well as how much wastes they produce. Also, when cycling WITH fish, you would have to constantly and nearly instantly replace the fish if one or more happen to die as this would constitute a major reduction in wastes in the tank.
The 'rule of thumb' that I found most common for dosing a tank with pure ammonia to start a cycle was to use a pipette (like the ones that come with some water test kits) to place 5 drops of ammonia per every 10 gallons of water. This will result in a reading of 5 ppm of ammonia. You will not actually see the entire 5 ppm since it will obviously take time for the ammonia to dilute and you will be running filtration on the tank which will reduce the reading slightly. The best bet is to do this on a daily basis, maybe every morning, and test the water daily, maybe at night or after work, until you see a well established ammonia reading. Then continue to do so until you see the ammonia levels begin to drop even though you continue to add ammonia. This would be a good clue to start monitoring both ammonia and nitrite levels.
Technical Reference:
Algone.com - Cycle your aquarium without fish! Fishless cycling!
From my experience, the using of fish to cycle a tank is out dated and unfair to the fish (ok, that is my opinion). The best fish to use for this are extremely hardy fish like molly, platty, or danios, to name a few. This creates some problems however for people with larger tanks as it would take quite a few of these smaller fish to even create a dent in the water quality.
I also learned from Jay that you should be able to 'transport' some of this bacteria from your other tank within the gravel and decor you state that you plan to do. This should also help get things started. I have 'cloned' quite a few tanks this way, however they are generally much smaller tanks (10 gallons) that I clone using one of the filters from my larger, main tank (55 gallon) and have had some great results.
Still, you should keep testing you water regularly until you are confident that your water is ready for fish. I assume that you are planning to allow your bala sharks to grow in this tank and if so, I would LOVE to see some pictures of them as they get bigger!
