New tank new bulkhead leaking!

[Sshannon]

For point of clarity why couldn’t one use aquarium safe silicone sealant?

Silicone sealant does not seal gaskets to plastic and glass very well. Silicone lubricant helps rubber gaskets sit better on surfaces under friction generated pressure. The gaskets creates the seal, the Silicone lubricant helps the gaskets do this better.