One-time star manager Bill Gross is leaving. The case for choosing an index fund for your bonds has never looked better.

For many bond fund investors, star fixed-income manager Bill Grosss sudden leap from Pimco to Janus is a moment to rethink. Grosss flagship mutual fund, Pimco Total Return long seemed like the no-brainer fixed-income choice. Over the past 15 years, Gross had steered Total Return to a 6.2% average annual return, which placed it in the top 12% of its peers. And based on that track record it became the nations largest fixed income fund.

But much of that performance was the result of past glory. Over the past five years, Pimco has fallen to the middle of its category, as Grosss fabled ability to outguess interest rates faded. It ranks in the bottom 20% of its peers over the past year, and its return of 3.9% lags its largest index rival, $100 billion Vanguard Total Bond Market, by 0.5%.

Nervous bond investors have yanked nearly $70 billion out of the fund since May 2013. Those outflows are driven not only because of performance but also because of news stories about Grosss behavior and personal management style. Still, Pimco Total Return holds a massive $222 billion in assets, down from a peak of $293 billion, and it continues to dominate many 401(k)s and other retirement plans as the core bond holding.

If youre one of the investors hanging on to Pimco Total Return, youre probably wondering, should I sell? Look, theres no rush. Your portfolio isnt in any immediate trouble: Pimco has a lot of other smart fixed-income managers who will step in. And even if you cant expect above-average gains in the future, the fund will likely do okay. The bigger issue is whether you should hold any actively managed bond fund as your core holding.

The simple truth is most actively managed funds fail to beat their benchmarks over long periods. Grosss impressive record was an outlier, which is precisely why he got so much attention. Thats why MONEY believes you are best off choosing low-cost index funds for your core portfolio. With bond funds, the case for indexing is especially compelling, since your potential returns are lower than for stocks, and the higher fees you pay to have a human guiding your fund can easily erode your gains.

Our MONEY 50 list of recommended funds and ETFs includes Harbor Bond, which mimics Pimco Total Return, as an option for those who want to customize their core portfolio with an actively managed fund. When issues about Pimco Total Return first began to surface, we recommended hanging on. But with Gross now out of the picture, we are looking for the right replacement.

If you do choose to sell, be sure to weigh the potential tax implications of the trade. Here are three bond index funds to consider:

*Vanguard Total Bond Market Index, with a 0.20% expense ratio, which is our Money 50 recommendation for your core portfolio.

*Fidelity Spartan U.S. Bond, which charges 0.22%

*Schwab Total Bond Market, which charges 0.29%

All three funds hold well-diversified portfolios that track large swaths of the bond market, including government and high-quality corporate issues. Which one you pick will probably depend on whats available in your 401(k) plan or your brokerage platform. In the long-run, youre likely to get returns that beat most actively managed bond fundsand without any star manager drama.