Dyfed-Powys Police said its officers made arrests relating to controlled drugs at the dance party near Llanddewi Brefi over the bank holiday weekend.
Local people and councillors have called for action to ensure more raves are not held.
Organisers of the event had relayed the remote location to people via text and email rather than social media.
Police said they became aware of a "large gathering" late on Saturday, 28 May but because it was already on a  "a very large scale" the decision was made not to break up the party.
Instead, officers stayed at the event to ensure more people could not enter the site.
The police helicopter helped to gather intelligence and evidence and arrests were made.
Llanddewi Brefi councillor Rhodri Evans said: "I have had quite a few people in Llandewi expressing their concerns - people driving through the village at very high speeds and perhaps putting people in danger."
He added that the area was "quiet and peaceful" and villagers wanted to ensure more raves were not held.
Officers have urged landowners to be vigilant to people enquiring about their land in the guise of hiring it for apparently acceptable activities such as gymkhanas and scouts and guides events.
Police are investigating after about 2,000 people turned up for a three-day illegal rave in Ceredigion.