Added sand, now water is cloudy

Did you prewash the sand before adding it to the tank?

That's the reason why then. Won't gp away until you do. The silt mixed in with the sand needs to be washed out by putting in a bucket, fill with hose mix it vigorously and dump the water until it is clear.
Easy to do with 5gal buckets. Should videos of how to wash sand on YouTube.

I just set up a 40B and 55L with pool filter sand, water was rough for 3 days, its normal with sand especially if you dont rinse it prior to filling the tank.

LaPrice said:

No, i had heard that before but i was unsure how to actually do it

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Get a 5 gallon bucket; fill about a quarter of the bucket with sand; Fill bucket about 90% full with water running hose wide open; turn off hose and wait about 10 seconds, then dump out as much water as you can; repeat this water filling/dumping process about 5-6 times then add this sand into the tank. Fill up bucket with new batch of sand and repeat entire process again with new batch.

Since your sand is already in the tank, just leave it alone and after a several months of water changes and all the fine floating sand getting trapped by the filter pads, water should eventually go clear.

When I set up my 75gal 2.5years ago, I did it in Feb and it was just too cold for me to do the rinsing, so I just added the sand unwashed into the aquarium. By the summer, it was hardly noticeable