ADA soil smell??

I have my 95 gallon tank setup for 4 months now. And the surface always oily no matter how many water change I did,they keep coming back.Also it has been smelly from the moment I setup this tank.Recently I just put 4 juvenile discus in this tank. My question is: Does this odor harm my fish?Any negative effect toward my fish?

 

HI there I'm not sure what kind of small it is.But the oil is from nitrification which is normal no worries

 

You want to make sure that there is enough water agitation. That should keep the surface from staying oily

 

liangzI it smells like earth mud + other thing I can't explain.. ReCause5764 I have no problem if the surface oily,I'm just wondering if it harm my discus and other fish

 

Well unless someone with more experience can school me on this, from my understanding it can. You need water agitation to have good gas exchange. That what's going to give your discuss the oxygen they need. If your surface is oily I don't think they're getting that. An air stone will solve this problem. Or your filter might be able to do it if you can point the outputs up, depending on your filter.

 

I have a built in filter,it has waterfall effect,I think that should be enough for aeration