Hi Marli,
Yep, surely looking forward to my trip. 
Certain countries may get visas upon arrival, (I didn't see Belgium listed, so it's best to get one in advance), and some others don't need one at all. Here is info for those countries eligible for arrival visas:
How recent is your source, Marli?....unless an date is mentioned, it's sometimes hard to know how recent info is on websites....
This is what I found on the Wallecea website. I'll be doing a cruise with them (http://www.wallacea-divecruise.com/info.html)
Other Practical Information
- Visas:
Since January 2004, a tourist visa is necessary for most visitors of Indonesia*. For citizens of various countries it can be get in the embassies or consulates, and also at your arrival at the entry airport. However, we not recommend this last option due to long waiting time.
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* Currently, the following 35 countries are eligible to pay US$25 for a 30 day visa or US$10 for a 7 day visa upon landing in Indonesia: United States, Australia, South Africa, Argentina, Brazil, Denmark, United Arab Emirates, Finland, Hungary, United Kingdom, Italy, Japan, Germany, Canada, South Korea, Norway, France, Poland, Switzerland, New Zealand, Taiwan, Belgium, Saudi Arabia, Kuwait, Spain, Portugal, Russia, Egypt, Austria, Qatar, Ireland, Maldives, Luxembourg, China and India.
Meanwhile only 11 countries and territories are eligible for a "Visa Free" facility, they are: Thailand, Malaysia, Singapore, Brunei Darussalam, Philippines, Hong Kong SAR, Macau SAR, Chile, Morocco, Peru and Vietnam.
Citizens of all other countries must apply for a visa before their trip to Indonesia!
This is what's on the North Sulawesi Tourism Promotion Board, Indonesia: (http://www.north-sulawesi.org/visa.html)
Effective February 1, 2004, Indonesia has introduced wide ranging changes in the national visa-free and visa on arrival system. We've tried to summarize those changes here for your convenience.
Visa Free on Arrival
In the past the nationals of 48 nations were given a 60-day stay (visa free) upon arrival at an Indonesian international gateway.
Under the new rules effective February 1, 2004:
• Only 11 countries and territories are eligible for a "Visa Free" facility, they are: Thailand, Malaysia, Singapore, Brunei Darussalam, Philippines, Hong Kong SAR, Macau SAR, Chile, Morocco, Peru and Vietnam.
• Nationals of the aforementioned countries and territories will be issued with a 30-day stay permit without charge upon presentation of a valid passport with 6 months remaining validity.
• The Visa Free Facility is not extendable or convertible into another type of visa.
Visa on Arrival (updated July 2006)
Nationals of 52 countries are able to obtain a "Visa on Arrival" processed at the gate of entry following the payment of an official fee: Argentina, Australia, Austria, Bahrain, Belgium, Brazil, Bulgaria, Cambodia, Canada, Cyprus, Denmark, Egypt, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, India, Iran, Ireland, Italy, Japan, Kuwait, Laos, Liechtenstein, Luxembourg, Maldives, Malta, Mexico, Monaco, New Zealand, Norway, Oman, People's Republic of China, Poland, Portugal, Qatar, Russia, Saudi Arabia, South Africa, South Korea, Spain, Switzerland, Sweden, Suriname, Taiwan, The Netherlands, United Arab Emirates, United Kingdom, United States of America.
I made a call to the Indonesian Embassy in Belgium and they confirmed Belgian citizens can get a VOA (as is mentioned on the website of Belgian Foreing Affairs)