That green filter looks like an Ehiem 2260/2262 canister, which is a GREAT filter..if it's still working.
looks like when you were messing around the gravel you kicked up a lot of debris and causing ammonia to rise then the filter is converting all the ammonia to nitrite then nitrate, so you seeing some ammonia (caused by all the stuff you kicked out from scooping the gravel manually, if you siphon them then this shouldn't happen since you will be removing them directly out of the water) 0 nitrite (the bacteria is doing great job at converting all the nitrite into less harmful nitrate) and high nitrate (can only be removed by doing w/c).
so frequent small water changes and siphon out as much crap as possible, stop feeding the fish until water is back to control, that's pretty much all you can do now.
the tank looks like it could use a good clean up too, wonder when was the last time any maintenance was done on the tank/filter. would be a good idea to clean the filter too, just make sure you clean it under tank water and not tap water so you don't kill of the good bacteria.