We have a 55 gallon tank with a watchman goby. We didn't see him for the first two weeks. After that then we saw him every day. I hope you have the same luck.
Be sure you test you water with a TDS meter before you purchase an R/O system. We purchased an r/o and it blows through filters and even the membrane after a few hours. Our TDS before the r/O is off the charts (890). Now we are stuck with a system that we can not even use.
The advice that I wish I would have liked to have followed was to buy what you will need not what is the cheapest. We purchased 2 different tanks, 3 different lights and 2 different protein skimmers before we got what we actually needed.
We had the same problem. We purchased 3 sand sifting conchs. We also purchase these packs that went into our sump called Algone. It worked really well, also.