I have a 75 gallon saltwater tank that is 6 weeks old just starting . cycled my tank for 1 month before added 3 blue chromis 10 blue leg hermit and 10 snails and now have this orange rust color on my base rock inside of tank walls on my sand i have never used tap water i have a r.o. in my house i have tested my r.o. and its below 10 ppm new filters and all i have done saltwater before and not seen this my levels are all fine let me know if you know so i can learn more