doctorhydrogen

I'd run Deglamer or Unravel the Aether over Naturalize. Stuff in the graveyard is a lot easier to get back into play than stuff shuffled into the library, plus it hits Theros gods, Darksteel whatever, Blightsteel Colossus, etc.

I'd run Expedition Map somewhere here (maybe over Burnished Hart). Worst case it'll fetch whatever land you need, but it can snag Coffers or Urborg if need be. Well worth it. For that matter I'd find a slot for Tolaria West for the same reason.

With all those fliers I feel like Coastal Piracy and Bident of Thassa would draw more cards more safely than Slate of Ancestry.

Will all those creatures Lurking Predators would do good work.

I know it costs 7 mana, but Dismiss into Dream is pretty amazing in Derevi. Forcing your opponents to sacrifice all the dudes you tap is pretty useful, but beyond that they can't equip them, give them counters, add enchantments, etc. Seriously, it wrecks board states with Derevi as the commander, no joke.

I'd find a slot for Greater Good. It's just generally a useful card, but because Skullbriar gets fat, stays fat, is cheap and has haste my friend who runs him in a deck sometimes just saccs him to draw cards and replay him. Recasting him for 6 or even 8 if you draw a dozen cards off it is usually worthwhile. Plus it's a good way to get stuff like Filth or Brawn into the graveyard.

Solidarity of Heroes wins games in +1/+1 counters decks.

Give Essence Harvest a look It's become a joke in our playgroup how strong the card is in my friends Skullbriar deck and in my Jenara +1/+1 counters deck. I don't think I've ever seen it dome someone for less than 10, and I've lost count of how many times I've seen one person die to Jenara or Skullbriar and had the third person think they could win next turn only to see an Essence Harvest for 22 or something stupid kill him in the second main. Seriously, it's amazing in these decks, and you look like a genius for killing people with a common nobody has ever even bothered to read.

I'd find a slot for Corpseajack Menace here.

Doubling Season would be amazing, and Hardened Scales is really great too.

Shizo, Death's Storehouse gives one more way to give Skullbriar evasion, and aside from Blood Moon-type effects it doesn't have much downside.

Skullclamp those snakes, son!

You've probably got enough creatures that Lurking Predators would do good work.

Lurking Predators would love this deck.

Hall of Gemstone and Primal Order are pretty great in mono green.

I'd run Constant Mists over Fog. Worst case it's a Fog that costs 1 more to cast, but having the upside of buying it back 4-5 times to end the game is well worth it.

Primal Order and Hall of Gemstone are brutal cards in mono-green.

Makes sense.

One minor last one, Regrowth is strictly better than Revive, and it's under a buck and was just reprinted in I think the Theros dual deck. It's not the kind of change I'd worry about too much, but if you have one lying about there's no downside to swapping it out and there's a little bit of upside if you want to bring back Wheel of Fortune or something.

Dissolve is strictly better than Cancel.

I'd run Deglamer or Unravel the Aether over Naturalize all day every day. I reject the notion that your Theros gods and Darksteel whatever and Blightsteel Colossus should be allowed to remain in play or that you should be able to use graveyard recursion to get something back when I deal with it.

Hinterland Harbor and Yavimaya Coast are both relatively cheap. I'd run them over the Vivids. I'd get a Reliquary Tower, too. If you don't draw enough cards to need a Reliquary Tower then you aren't drawing enough cards :)

Me personally I'd go all-in on the +1/+1 counters theme and run stuff like Vorel of the Hull Clade, Guilder Bairn, etc. But that's me; I kinda hate goodstuff decks and I'm a slave to gimmicks/themes.

If you want to increase your chance to hit stuff with Predators and Primal Surge and have less chance to take Ruric Thar damage you could replace the following:

Rampant Growth--> Sakura-Tribe Elder
Creeping Corossion--> Bane of Progress
Explosive Vegetation--> Seedguide Ash or Wood Elves
Exploration--> Courser of Kruphix or Oracle of Mul Daya

Some of those aren't exact, but Rampant Growth for Sakura-Tribe is the same casting cost so that one at least would be a good switch. Plus the Elder is like a twenty cent card.

All those creatures would love Lurking Predators.

A successfully cast Primal Surge could put 50 permanents in play pretty easily here.

Bower Passage makes a good amount of your dudes unblockable.

Hunter's Insight and Hunter's Prowess will draw you STUPID amounts of cards here.

I'd run Deglamer or Unravel the Aether all day over Nature's Claim. One extra mana to not give your opponent life, make it harder for them to recur the target, and be able to hit Theros gods and Blightsteel Collossus or a Darksteel Forge is worth one extra mana.

Find a slot for Savage Ventmaw. That thing is like a free spell every turn.

No Quicksilver Fountain? That's one of the biggest unfun cards in monoblue.

Also, if it was me I'd yank both your artifacts and replace them with artifact hate. You've only got two, and while they're both useful, they're not backbreaking. Something like Stony Silence though, there are decks that one card would literally destroy, and almost everyone runs Sol Rings, etc. It's never going to be a dead card and in lots of cases it's going to be a card that can make people scoop. Just a thought, but you're never going to laugh manically knowing you've just won the game top-decking a Skull of Orm, and there are times when the guy next to you has four mana rocks out when top-decking Stony Silence is GG.

Similarly City of Solitude is great. You have no instants so why do you care, but it shuts down counterspells and combat tricks which is amazing. Never worry about a mid-combat Cyclonic Rift or Aetherspouts again.

Also, successfully casting a Primal Surge in this deck is probably going to put 50 permanents into play. That ain't bad.

Probably Gift of Immortality or Venomous Fangs. Your other auras will fall off when Krond dies even if Gift brings him back, so it's really not doing that much good, and if you've got an aura or two on Krond anything blocking or blocked by him is probably dying anyway.

Ancestral Mask ends games.

Spear of Heliod is probably slightly better than Angelic Voices just because of the tap effect.

I'd probably run Brave the Sands over High Ground. One extra mana to cast to give all your guys vigilance seems worth it imo.

Pearl Medallion would probably save you a ton of mana, too.

I'd at least find room for a Mass Calcify. It's a good value card in mono-white and in some games can be an ender.

No Hero's Downfall? In mono-black it's strictly better than Murder.

Kothoped has been amazing so far in my Silumgar all-fliers deck, I think you'll be happy with him.

I actually wound up taking apart my Kaalia deck because it just got so obvious to everyone that if I attacked succesffully and got rolling I probably won, and if I didn't I couldn't do anything, so basically any removal was saved for me. I even wound up running Red Elemental Blast and Pyroblast to deal with counterspells. It was just too frustrating to play a deck so reliant on the general being on the field a turn to do anything. That's probably largely a meta issue though.