NEW YORK (

TheStreet

) - Wall Street traders predict that

Citigroup

's

(C) - Get Report

1-for-10 reverse stock split will be bad news, causing a dive in trading volumes that will hit the bottom lines of some brokers.

"I think Citigroup volume will be down over 90 percent," said Eric Noll,

The Nasdaq OMX

executive vice president of transaction services at the Security Traders Association of New York Conference on Thursday. "I think the spreads will tighten and overall

market volume may dive as much as 20 percent."

Citi announced a 1-for-10 reverse split of its common stock earlier this month that will be effective on May 6, 2011. The reverse

split will reduce the number of outstanding shares of Citigroup from 29 billion to approximately 2.9 billion.

The drop in available shares, along with the rise in price, will mean that traders, off-exchange venues like "dark pools" and high-frequency shops will no longer be able to embrace the bank's cheap and plentiful stock as a tool for rapid-fire trading.

Bryan Harkins COO of

Direct Edge

said he believes that dark pools will experience the most downside of the reverse split since they have been the most prolific traders of Citi's cheap shares.

Traders also say it's unlikely that another cheap, but solid stock, is available to take the bank's place in the markets. "Citigroup was a unique stock that was the result of the financial crisis. I think if there were another stock that would take its place, traders would already be on top of it," said Joseph Mecane, executive vice president of

NYSE Euronext

.

--Written by Maria Woehr in New York.

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