no, its not or else u wouldnt be seeing ammonia
if ur saying u dont want to get the melafix on the oscar side, then are you saying the divider has no holes and is siliconed in place?
how does the whole tank get filtered without getting melafix on both sides when u only use one filter??
why do u even have a divider? fish can usually fend for themselves and should be rehomed if they cant
ur tank is filled like 2/3 of the way tops and is divided by a water proof glass sheet, ur oscars are not in a "112", which is actually called a 110, they are in like 50 gallons tops
it doesnt matter how many gallons your tank can hold if the water isn't in it, and i know ur getting like a lid or something
best remedy is getting a hob added to ur tank and putting some quilt batting for mech, then pack it with bio like eheim substrat pro, biomax or something similar
edit: wtf i just watched ur video the blue flash (aureus) has 0 filtration on his side of the divider, he's living in pure ****