am I overstocked?

what type of synodontis (upsidedown cats) do you have? these fish (for the most part) get HUGE- in fact im looking for someone to take my synodontis once it gets bigger. These fish get HUGE like the size of a 10gal w/ fins attached
hopefully, the ones you have dont get as big as i figured out that mine will get

also keep an eye on the guppies and gouramis- sometimes gouramis will attack guppies b/c they look like another asian fish w/ their flowing fins, and for the apple snail, watch your plants and make shure it has plenty of food

Yeah, in addition to the catfish, depending on what they are, you will also be way overstocked once the kissing gouramis get bigger, they can get up to a foot long, and need at least 55 gallons. But if you got rid of them, and the catfish, depending on if they will also get too big, you would be alright! Also, do you have plants? I'm wondering why nitrate is 0.