F2 Fertilizer Recommendation?

[Jobu183]

Anyone have a recommendation for an F2 fertilizer?

I have been using this Coral Ranch F2 from Amazon, however, similar to some of the reviews, I've had to double or triple the dose in order to not have my culture go yellow. Would like to try something different.

 

[Subsea]

 

[Mr. Mojo Rising]

I use Guillards F2