You do not need to hit any minimum Fish Points weekly to receive your fixed cashback. However, there's a required Fish Points (FP) that you need to hit yearly to renew/maintain the Platinum ranks as per the table below.
In order to reach certain Platinum ranks (promotion), further FP needs to be collected on top of the renewal amount from the lower Platinum rank as per the table below.
Example: To get from Platinum Shark to GGPlatinum, you will need to collect at least 5 million FP in 1 year.
To reach Platinum ranks that do not have promotion requirements, you will be required to reach the Fish Buffet rank which you can then switch to that Platinum rank.
Example 1: From Platinum Fish, you will need to switch to Fish Buffet and reach at least Bronze Whale 3 to be able to switch to Platinum Octopus.
Example 2: From Platinum Octopus, you will need to switch to Fish Buffet and complete Gold Whale 1 (earn 120,000 FP within 30 days) to be able to switch to Platinum Whale.
If you fail to collect the required points in one year, your rank will drop down to a lower Platinum Rank. For example: Platinum Whale will drop down to Platinum Octopus.