Trace amounts of sand on the bottom of my pool

So over the last few days I've been vacuuming my pool of all debris that falls into it getting it ready for the swim season. One things I've noticed is small particles of sand grouping up on the seams of my liner.

At first I thought it could have been Algae again but it's brown in color and any sort of movement near it swirls it up into the water. I'm going to take a guess and say it's sand.

Now my guess is when I backwashed my filter last year with filter cleaner prior to closing it I forgot to rinse it to settle the sand. I likely went Backwash > Waste > Close.

Could this just be residual sand from that backwash? Do you recommend I do another full vacuum of the pool, backwash it for 60 seconds then rinse for 60 seconds? It's a very minor annoyance but the pool is going to be my baby for the summer.

My guess is that it is most likely just dirt. I see the same thing in my liner pool. When you vacuum, the movement of the vacuum head causes some of the dirt to get into the suspension of the water. Then, later when the water quiets back down, the dirt drops back to the floor. You have to move the vac head REALLY slowly to avoid this and even then, it is impossible to prevent it totally.

When you backwash, always rinse.

What size is your pump and what size is your sand filter (how many lbs of sand does it hold)?