I found another online nutrients calculator yesterday and, in my opinion, it ranks very well compared to Chuck Gadd's (http://www.giveawayoftheday.com/soft/523956/), FertFriend (http://www.fishfriend.com/fertfriend.html) and APC's Fertilator (http://www.aquaticplantcentral.com/beta/fertilator.php).
What dose to reach a target / results of a dose (all above calculators do that):
Yet Another Nutrient Calculator (http://calc.petalphile.com/)
Online and downloadable charts of concentration vs time (this is the novelty here)
Concentration of Stuff vs Time & Uptake using Estimated Index (http://ei.petalphile.com/)
Pros:
- compares your dose against Walstad, PPS-Pro and Estimative Index recommendations
- very complete in terms of composition of the results
- charts long-term effects of your dosage vs time and amount of water changes
Cons:
- doesn't include commercial bottled fertilizers (Seachem's, Kent's, Tropica's, Nutrafin's, etc)
- poor graphic design :P
Enjoy !