I want to store a hash (of a tweet) in a way that is :

• Censorship proof
• Public
• Unchangeable
• Persistent
• Non centralized
• Less expensive as possible, obviously free if possible

Technology offered by the blockchain seems to fit my needs.

Since I don't want to run my own blockchain because I didn't find a way to do it for free (or does it makes sense to run my own blockchain on my own server ?). After reading on the subject, I came up using an existing coin (Bitcoin ?) and as you may guess to the OP_RETURN field in a transaction. But storing my hash in that field is really appropriate ?

Can't I use other coins for that, or create my own coin ?

Since I will store lots (3k/day) of tweets, will it not be expensive to do so ?