I have a suggestion...
Building off of your idea of a "Grabber/Leech that attaches to objects": The Holdfast zooid.
Max Health: 10 when un-anchored, 15 when anchored
Range: 3 (similar to Leech zooids)
Nutrition Capacity: 4
Energy Regen/Second: 3 when un-anchored, 10 when anchored
Ability: Anchor (Energy Cost: 30, Cooldown: 1) - Attaches itself to a nearby object. Doing so greatly increases the energy regeneration and health of the zooid.
Base zooid cost: 4 Nutrients
Great for making sessile creatures, this zooid is able to sprout "roots" to attach itself to any object (yes, even eggs and spike balls, though the latter is risky). Since sacrificing movement is quite a large trade-off, this zooid offers exceptional energy regeneration compared to other utility zooids when anchored, while also making sure it is not easy to destroy. Also, rather than requiring a constant energy cost for the zooid to hold, a better alternative would be to make it be a toggle ability, ie. spend 30 energy to anchor, and another 30 if you wish to un-anchor.