Personally I think Nissa's Pilgrimage is better than Kodama's Reach because of the potential to get 3 lands if you have a few sorceries in your graveyard already. I also think Hydra Broodmaster is one of the better hydras since it's monstrous can fill the board up with tokens. Maybe replace some of the Managorger Hydras with some. Your deck will also have trouble with removal and flying, so you can add Ulvenwald Hydra for its reach and cards like Blossoming Defense to protect your hydras from spot removal. I <3 hydras, this looks like a fun deck.

Oh, Nykthos, Shrine to Nyx is a must have land for decks like this

Oran-Rief Hydra might be a good card for this because it is constantly grwoing as long as you have a land. I would take out Mistcutter Hydra because while it has protection from blue, it needs other creatures to keep growing. Vastwood Hydra would pair well with Scourge of Skola Vale. You could encorporate this by simply taking 1 card off of some of your other hydra's that have 4 cards.

Hardened Scales would make this pretty nasty... especially on the managorger

No mana dorks for quickly using Kalonian Hydra? I can drop him turn 3 with some elves. Arbor Elf, Elvish Mystic, Llanowar Elves, Priest of Titania, Elvish Archdruid.

I would recommend ordeal of nylea for the land ramp to help with your higher cost hydras and to add +1/+1 counters.

Rofellos, Llanowar Emissary is nice in monogreen Hydradecks :3