Anymore room in my tank?

No its over crowded already and the comet goldfish will get around 6-8inches.

Even if the comet goldfish gets around 6-8inches they still atleast need a 12-20gallon tank each because of bioload and size. But mainly all goldfishes need atleast 25-30gallon tank with a good proper filter.

And at the same time goldfishes are coldwater, but you still need a atleast 24 to 30gallon tank for the tropical fish you have now and have your new cory and/or oto that you want or a 45gallon for a nice school of cory(6)(They are best kept in this number or more).

Yes, get rid of the gold fish - not only are they very messy, and grow huge (way too big for the tank, the above mentioned 8" is very conservative - any common goldfish can get well over a foot in the right environment), and not only are they cold water fish that and will likely cause problems for your other fish at some point, but getting rid of that one fish will also open up lots of room for other, more suitable types to your tank.

Once you lose the goldfish, you can add 3 or 4 more cory catfish without any issues and have them in an appropriate school, and you can even add a couple of otos too - but since you already have a cory, more of them should be your prime objective.

When you say nitrite and ammonia levels are acceptable - you mean 0 right? Only 0 is acceptable for these.

No, there is no more room in your tank. Remove the goldfish because he'll grow to over a foot long. Goldfish are also coldwater, and your other fish are tropical. If you remove the goldfish, then you can get another cory or Otocinclus.

~ZTM

overstocked now,

that goldfish is movng to another tank soon right? something like a 55 gallon with a canister filter.

Im petty sure that your water parameters arent correct either with that many fish and that filter.

So you will need to move that goldfish asap, but then you still cant add anything else as your still alittle overstocked.

Goldfish will get big, comets are the second largest type of goldfish, they will reach over 24 inches. and you will need at least 55 gallons with a canister filter.

edit: there are no stocking rules. 1 goldfish per 10 gallon isnt correct and the 1 inch per gallon for tropicals isnt correct.

All of those "rules" have been outdated, please stop passing it along, as it is outdated........

No! You have no room, in fact you're overstocked as it is. That goldfish needs to come out of there and go into a minimum 20 gallon tank all of its own (and you will need bigger later). The 10 gallon is fully stocked as it is with just the danios and cory. Goldfish are coldwater fish and danios are tropicals and they have different water requirements, but even if this weren't an important issue, that goldfish needs a lot more room or it's going to kill itself and everyone else in that tank.

First of all you are going to have to make a tank change if you keep the goldfish and you could get another cory but don't get an oto because they are territorial. But no matter what you need at least a 20 gallon tank for the goldfish by itself because it will grow 8 inches to a foot.

EK

10 gallons per three inches of goldfish is a good rule. What do you consider an acceptable level? Ammonia and nitrites should be at a constant 0 to be acceptable, anything above that means the tank is not fully cycled. Once the tank is cycled you should never see these chemicals spike again, unless you overclean. Nitrates should be under 10 ideally. Corys and otos are schooling fish, so if anything, add another cory to your existing one rather than getting a single oto.

Your tank is already well overstocked. 10 gallons is a tiny home. The comet will out grow it just by itself.