build-up on first stage

Hello,
I recently went diving and after returning home and washing my equipment I noticed there was some green build-up on the first stage, the build-up does not wash off with just running water, and is not mossy in nature, it feels hard to the touch. Has anyone encounter this? Any ideas what it is? how to get rid of it? prevent it from happening again? What caused it to happen on the first place?

Sorry for all the questions but I would like to have this first stage last a while.

In case it matters, it is an oceanic first and second stage combo. Bought less than a year ago, used for a trip to the keys where we did about 10 dives, cleaned and stored in dry storage after trip. It has not been serviced.

Ive taken and included some pictures in hopes that itll help you guys help me figure out what it is. Sorry about the bad picture quality.

Well the color is an indication that it is copper oxide. Is your regulator chrome plated brass? Exposed brass will do just that. A weak acid like white vinegar diluted to 50 volume percent will take it off. Heat will make that go faster. But...it will likely come back over time. Rinsing well in fresh water will slow down the rate it comes back. It is not overly alarming.

Salt water is being trapped under that plastic saddle against the metal 1st stage. Rinsing is not sufficient to remove it. It take a soaking of a couple hours or more to dilute that salt. The good news is it does not present any performance problem and can probably wait until service is required to be thoroughly removed. But soaking will be required to keep it from getting worse and from reoccurring once it is cleaned.

also remove the hose protectors - they just trap salt water and don't really protect against anything

Verdigris is a common on brass regs that are dove in salt water. Soak your regs for at least five minutes in fresh water after your diving is done to minimize it. It's not a big deal unless it's inside the reg. Look at the sintered bronze filter on the inlet. If it's green, you should go ahead and have your reg serviced.

As it is, I would still dive it. you can use a brass brush to make it look a bit better before you do have it serviced.