Multipools switch between different altcoins to maximize miners profit.
The criteria for switching to different altcoin than the one currently mined by the pool is by continually calculating the most profitable altcoin.
Two key factors are involved in the algorithm that calculates profitability, the block generation time and the current price of the supported by the pool altcoins on the exchanges.
- The difficulty of mining the coin
- The exchange rate between coins
- The block generation time
- The hash rate currently on a altcoins network
To make sure you don’t need many different wallets for all possible minable coins, almost all multipools now automatically exchange the mined currency to a coin that is accepted in the mainstream (usually bitcoin).
Using this method, because the "most profitable" coins are being mined and then sold for the intended coin, you receive more coins as a miner in the intended currency than you would by mining that cryptocurrency solo.
This method also increases demand for the intended coin, which has the side effect of increasing or stabilizing the value of the intended coin.
Multipools are very handy if a user is uncertain about which coin is best to mine at any given time and for cryptocurrecny newcomers.
However, because the cryptocurrency that was just mined is typically immediately exchanged for another one, the price of the mined cryptocurrency can often end up declining slightly.