Is this tank overstocked? There are many baby Goldish and a couple of adults (some not visible in the dark area). According to some people it should be OK, others say that goldfish need 40gal (80l) per fancy goldfish, so I used to keep two fancy Goldfish and 2 Pangasius fish, but my dad buys me a lot of goldfish.
And many people said that the growth will be stunted, but the local fish store said that it is okay and they also kept a lot of goldfish in a small aquarium for sale. Not to mention my local fish store kept an adult Flowerhorn on a 2.5 gal tank without a lid, and it's not even for sale.
edit: there are 9 baby goldfish, 7 adult goldfish,2 pangasius , and 2 common pleco, the first day i got the baby goldfish 3 got sucked into the filter, after that i cover the intake with sponge