Magellan fund reopens after 10 years

"Just to get a little bit of money in every month is sort of what portfolio managers dream of," said Lefkovitz.

"This is just a fund that has been in redemption mode for years and years and has been steadily bleeding assets," he said. "I just hope that Fidelity is much more vigilant about monitoring asset growth."

Indeed, some investors are wary of funds that grow too large.

"Some people think that once you are in the multibillion dollar stage you are essentially a closet index fund. But it's proven that it's not," Jeff Tjornehoj, an analyst at fund tracker Lipper Inc., said of Magellan.

"This puts Fidelity Magellan back on your list of funds for considering," he said of many investors.

The fund, which is nearly 45 years old, isn't the only one fund that Fidelity had closed but the company says it doesn't have plans to reopen other big funds like the $81 billion Contrafund.

Not all fund managers try to avoid becoming huge. American Funds' Growth Fund of America has assets of about $185 billion and often earns praise from analysts.

And small-cap funds are much more likely to close to investors because it can be too difficult for them to move in and out of positions if selling a stock, for example, would cause the remaining shares to plummet.

But with small-cap stocks having fallen out of favor after years of outpacing large caps, small-cap funds are also finding room to reopen. The Aston/RiverRoad Small Cap Fund in December began allowing existing investors to add money to its fund after a year of barring any added money.

"You're seeing some of these funds start to ease back open," said Andrew Beck, the fund's manager, citing a recent pullback in small-cap stocks.