I'm not really familiar with that, but it seems like netting will just stop him from getting sucked through but not actually sucked up against it in the first place. It seems like being pulled against the skimmer and held in place would be even more damaging.
It seems like you need either a sponge to cover the intake or else something rigid and porous that can be secured around the intake without actually blocking it- something that will allow water in but keep the goby at least a couple of inches away from the intake. (There are very little shower caddies that have suction cups on the sides. That may work, but I'm guessing on that since I don't know where the intake is.)
Generally for a quarantine tank, bigger is better, but you are dealing with a nano, so it's not like you are going to be adding a giant fish in there. :lol: It's mainly a matter of being able to keep water parameters stable. A little uneaten food in a 30 gallon QT will probably not have an effect. A little uneaten food in a 5 gallon QT could be disaster. There's also trouble keeping the SG stable in a smaller water volume.
A for what you need, it's fairly basic. You need a tank- even a rubbermaid container will work. It doesn't actually have to be glass. You need some sort of HOB filter. A sponge seeded from your main tank can generally keep ammonia from spiking, but I recommend getting one of those ammonia locking products to be on the safe side. You may need some sort of air stone and pump to keep up oxygen levels since you won't really have much flow in there. You need hiding spaces for your fish. I use pieces of pvc, about $1 each. You also need a small heater. Although my QT had sand and rock to keep it more stable, it's easier for maintenance to have a bare bottom tank so you can siphon out the junk that settles on the bottom.
You don't need a light, sand, rock, or anything else that will make it a beautiful setting for your fish to hang out in. Actually, the less the better in case you need to medicate.
I also made a mark on the outside of my tank that was the top off line. I didn't fill my tank all the way to the top, and I could easily see when it needed to have a bit of fresh water added to keep the SG stable.
