Sure, they are ponzi. No 100% profit after exactly 20 days for real company.
This reminds me of the several of the well-known doublers. Most of these doublers are 30 days. Many of these doublers did survive for over 6 months, some even survived about 1 year. The last scammer of this type is ExpInvest (Expert Investment) with 200% after 30 days.

Look at polexinvest inc terms :

http://www.polex-invest.com/index-11.html

You agree to only invest money that you can afford to lose. You understand that in all investment arrangements past performance is no guarantee of the same future performance. Any investment can fail at any time. Please invest at your own risk.

Sounds fair so no ones going to complain about losing money as they have been warned.

Becareful, not many Ponzis tend to last long with an official warning :
http://www.ifsc.gov.bz/notices.html

WARNING NOTICE
POLEXINVEST INC.

It is notified for general information that POLEXINVEST INC. is not licensed by the International Financial Services Commission or any other competent authority in Belize to engage in the business of forex trading or any other international financial services.

All persons concerned are asked to take note and exercise caution.

GIAN C. GANDHI
DIRECTOR GENERAL
International Financial Services Commission

This ones going down soon so get out while you can.