This is possible, but there is a variation in terms of how much you stand to gain,it should be done through crypto currency (altcoins..etc)as opposed to fiat which is quite slow,the volume of trade should be considered and/or also the speed at which you convert due to price stablization should be considered,you wont stand to make a huge profit specially after late confirmation and withdrawal fees,so it is a risk altogether and also avoid scam cryptocurrencies
Sure, but it's only theoretical. I told about strategies and experience before. It is not possible without!
Also trading fiat is not possible without.
By the way, the trade volume comes from the people who trade a currency, no matter if fiat or crypto...
And also fiat money is volatile, it goes up and down by the time... Look at Russian Ruble, Dollar against Euro and so on...
And a profitable strategy means how you do things to profit from it. All the people here talk about arbitrage. But how they do it? I cant read...
They say mostly, they buy on one market cheap and sell on the other market for a higher price. Yeah this is right, but it is not all...
I say, the best kind of arbitrage is direct, you buy and sell at the same time! This means you need on each exchange some amount on balance. Sending money from A to B needs mostly to much time (after arriving the price difference could be gone...).
And my strategy works very good with less withdrawals. Look here at my picture, i do 10'000 trades and less than 800 withdrawals + deposits.
https://bitcointalk.org/index.php?topic=884520.msg11207338#msg11207338 And further there a more kinds of arbitrage, also direct but inner exchange! For example by using 3 markets or more, called 3 way arbitrage, 4 way arbitrage ans so on.
Lets explain a example in short. I buy some LTC with BTC. The LTC i use to buy DOGE. With the DOGE i buy XPL. And the XPL i sell for more BTC as i used to buy LTC.
But you have to calculate the prices before this steps! It is not possible every time. But i can do this 4 way example on cryptsy inner-exchange!
But also i can execute one or more of this steps on a different exchanges if the prices is more profitable and if i have coins on balance. It doesn't matter where i place my orders as long as i can await that they get filled.
There are so many altcoins and so many exchanges. I find every day a lot of good trades.
And a good trade means, i get 10%. Also i won't promise to much, but also 100%, 300% or much more is sometimes possible.
But 10% is a good rule of thumb as orientation. And even if not possible, with some trades i am lucky with only 3 %.
And then is there a option to do arbitrage with a time delay, and not by buying/selling directly! This you can do if you await that the price reach a level next hours, day or weeks. Or if there is request on the market which you like to use to profit from.
So lets summarize, arbitrage is possible direct or with a time delay. It is possible on the same exchange or different exchanges. And it is also possible by using only 2 or more ways/markets.
And all kinds are possible in combination together somehow.
The big advantage of arbitrage is, it goes mostly fast, you don't hold the altcoins for a long time!!
Only some altcoins maybe which you use as base currency, in the same way like BTC. For example DOGE and LTC are base currencys. And this are good altcoins, not so scammy like others maybe... Finally i say, trading bitcoins against altcoins and altcoins against altcoins, is much more profitable as using fiat to trade bitcoin!
Especially if you know an exchange where you can buy cheap 
Also Volume is not all for profitable trades!
Fees are very low for trding with cryptocurrency and withdrawals are fast in most cases!
