diff --git a/src/lib/turtle/InvManager.hx b/src/lib/turtle/InvManager.hx
index 0c50d0a..582dd0c 100644
--- a/src/lib/turtle/InvManager.hx
+++ b/src/lib/turtle/InvManager.hx
@@ -1,7 +1,5 @@
 package lib.turtle;
 
-import kernel.KernelEvents;
-import tink.CoreApi.Outcome;
 import kernel.log.Log;
 import kernel.turtle.Types.TurtleSlot;
 import kernel.turtle.Types.InteractDirections;
@@ -20,7 +18,7 @@ class InvManager {
 
 	private static function getInvState() {
 		var invState:InvState = new Map();
-		for (i in 0...Turtle.MAX_SLOTS - 1) {
+		for (i in 0...Turtle.MAX_SLOTS) {
 			var detail = Turtle.getItemDetail(i);
 			var spaceLeft = Turtle.getItemSpace(i);
 
@@ -87,4 +85,90 @@ class InvManager {
 		Turtle.selectSlot(slot); // TODO: handle error
 		return Turtle.place(dir);
 	}
+
+	private static function getSlotsForItems(invState:InvState):Map<Item, Array<TurtleSlot>> {
+		var rtn:Map<Item, Array<TurtleSlot>> = new Map();
+
+		for (k => slot in invState) {
+			if (!rtn.exists(slot.name)) {
+				rtn.set(slot.name, [k]);
+				continue;
+			}
+
+			var value = rtn.get(slot.name);
+			value.push(k);
+			rtn.set(slot.name, value);
+		}
+
+		return rtn;
+	}
+
+	/**
+		Cleans up turtle inventory. Moves items together.
+		This should be run in a turtle thread.
+	**/
+	public static function defrag() {
+		var invState = getInvState();
+		var items = getSlotsForItems(invState);
+
+		for (item in items) {
+			defragItem(invState, item);
+		}
+	}
+
+	private static function defragItem(invState:InvState, slots:Array<TurtleSlot>) {
+		// Sort slots by items inside.
+		slots.sort((a, b) -> {
+			return invState.get(a).count - invState.get(b).count;
+		});
+
+		var maxInSlot = invState.get(slots[0]).max;
+
+		// Loop from both sides. Move the slots with the lowest count into the fullest.
+		var topIndex = slots.length - 1;
+
+		for (k => slot in slots) {
+			if (topIndex <= k) {
+				return;
+			}
+
+			var count = invState.get(slot).count;
+
+			if (count == maxInSlot) {
+				return;
+			}
+
+			while (true) {
+				if (topIndex <= k) {
+					return;
+				}
+
+				var topCount = invState.get(slots[topIndex]).count;
+				var spaceInTop = maxInSlot - topCount;
+
+				if (spaceInTop == 0) {
+					topIndex--;
+					continue;
+				}
+
+				var transferCount = MathI.min(count, spaceInTop);
+				if (!Turtle.transfer(slot, slots[topIndex], transferCount).isSuccess()) {
+					Log.error("Failed to transfer items");
+				}
+
+				// Update invState
+				var topState = invState.get(slots[topIndex]);
+				topState.count += transferCount;
+				invState.set(topIndex, topState);
+
+				var botState = invState.get(slot);
+				botState.count -= transferCount;
+				invState.set(slot, botState);
+
+				if (count - transferCount <= 0) {
+					break;
+				}
+			}
+		}
+	}
 }