I would think that if the anole had plenty of escape options from the water bowl that it should be fine, however the toxicity of the frog is an area of concern. I'm not sure how toxic your treefrog would be to your anole, and how quickly the water could be tainted with the toxins from the frogs skin. However, if you do the rubbermaid idea, you can set it up so that you can remove it daily and replenish it with fresh dechlorinated water, thereby effectively removing any toxin buildup that may occur. It is a gamble, though, keeping two completely different species together, even though both the green treefrog and the green anole share much of the same natural range. I have kept anoles in the past, and have noticed definite aggression in males, however a 60 gal terrarium is a lot of space for both animals to find their own territories. The biggest issue I can see being a problem is the possibility of the anole mistaking the frog for food when it moves, and even though the frog is probably too big for the anole to eat (let's face it, anoles are not the biggest of lizards), it still can cause some damage to the frog's delicate skin should it happen to mistakenly grab it. Also keep in mind that frogs are very opportunistic feeders, and I have witnessed mine try to steal food from each other's mouths. If the frog tries to steal a cricket or something else from the anole, it could wind up getting accidentally bitten. Not to say that this will definitely happen, but something to watch out for. Good idea having a second cage on hand for the frog if need be, and good luck! I think interspecies tanks are cool, just not always the easiest to do.