Havent seen my clown goby for 2 weeks/Could I add another fish?

[Chris_Noles]

So the spot my clown goby usually hangs out at is now empty and I havent seen him for 2 weeks and doesn’t come out for food when I feed (he never did when I fed the tank even when I could find him). So could he be dead? My tank is a 25 gal and right now I have a clown, gramma and a banggai cardinal. Could I add another fish or would the tank be overstocked? I also run a nano skimmer and a carbon reactor.

 

[Rickybobby]

Do you have a filter chamber or a sump?

 

[Chris_Noles]

Do you have a filter chamber or a sump?

I do its an AIO tank and I haven’t looked in the back yet