I think in the past the recommendation to go larger for people new to the hobby made sense, but the old adage that nano tanks are harder just isn’t true anymore. Biocubes are not the most advanced setup, I wouldn’t say it’s a beginner’s setup, it’s a simple setup, but they are a beginner, so… Plus, Biocubes are almost infinitely upgradable/modable. Biocubes are just about perfect for someone just starting out. You’re right that the coralife skimmer isn’t great, but if water changes are kept up, a protein skimmer isn’t necessary. I currently have a Nanocube, which is similar to a biocube, and I’ve had tanks of all sizes and have kept reef tanks for over 20 years, and I can tell you with certainty that the Biocube is a great, maybe even the best, choice for someone just starting out in the hobby. They’re easy to upgrade and easy to sell if you want to graduate to a larger tank. I guess I just don’t understand how it’s helpful to tell someone to return a tank they’ve already put water in and to buy a tank at least 4 times larger at over 4 times the cost. It’s elitist and unnecessary.If you’re able to return it I recommend a Red Sea or water box tank. Larger than 100g. I don’t recommend smaller tanks and or/nanos for new reefers. You have a very novice set up. I recommend looking into higher end equipment. That coral life skimmer doesn’t do anything. I would get a real salinity tester like a refractometer. I also recommend you try and obtain actual live rock that’s been sitting in an established tank for at least a year.
I do agree with you on the live rock though, at this point they’ve already got a tank full of rock, so I’d recommend adding a pound or two of quality live rock.