Just to be sure, do you know what's in the tap water? Most water is treated with chlorine or chloramine. Unless you know for a fact that your tap water is amazingly clean, use RODI.
Looks like you used live rock correct? Purchased locally, transferred wet, and put right into the tank? If so, then you will probably have little to no cycle. you will, of course, have all the fun that comes with a new tank like algae and diatoms. A good test is to dose pure ammonia, no scents or additives, to 0.2ppm(I think, double check me on the concentration.) I good test is to have a seachem alert badge. You should see the badge turn a light blue and then go back to beige within 24 hours. Do this, of course, with no living creatures large enough to see in the tank.
So, good opportunity here. I just did a transfer myself. Did you properly QT your fish in the biocube? If not, since they've lasted this long, they likely don't have velvet but could very well still have flukes, ich, or bacterial infections. This is a great opportunity to confirm and remediate all of those conditions. Unless the new live rock came from a fishes system I'd let the new DT sit fallow for 76 days. On day 64 start the TTM method for your existing fish. Start with a FW dip between the biocube and the first TTM tank for 3-5 minutes and check for evidence of flukes. If you find evidence you can treat with prazipro in tanks 1 and 3. Check for white, stringy poop from any fish as well while they're undergoing the TTM. If you see any, you can treat in tanks 2 and 4. The TTM itself takes care of ich. You can read up on all of this in the fish disease section. There's some great information from people with significant experience.
Good luck!
