100 Gallon Tank Rancid water In SA cichlid tank - stressed out fish HELP!

Came home and noticed my SA cichlids weren’t excited to see me so I opened the lid and to my surprise the water smells rancid.. the nitrates are through the roof but nitrites and ammonia are normal. Doing a 50% water change and took out all the plants(which smelled nasty) and the rocks. Even with the new water being added(tested and good) it still smells. My cichlids are stressed out and so am I!! Help!!!

 

When is the last water change?

 

Last Wednesday I did a 75% — have been doing it once a week of 75% for the past few months. I’ve got an eheim and a FX6 filter in there. Minimal feedings. One green terrier, one severum and 4 barbs.

 

That seems strange then. If nitrates are high the usual suspects are the filter clean or water changes.

 

Perhaps there is something burried in the substrate rotting?

 

I changed my fx6 filter last week during the water change and then the eheim I did today. I use chemipure, carbon and zeolite.. nothing has changed with those. All fish are accounted for. Nothing in the substrate. I cleaned the rocks and put them back in. I’m going to trash the plastic plants because they smell horrible.
I just don’t know what it could be… should I do another 25% water change tomorrow and daily until the smell goes away?

I changed my fx6 filter last week during the water change and then the eheim I did today. I use chemipure, carbon and zeolite.. nothing has changed with those. All fish are accounted for. Nothing in the substrate. I cleaned the rocks and put them back in. I’m going to trash the plastic plants because they smell horrible.
I just don’t know what it could be… should I do another 25% water change tomorrow and daily until the smell goes away?

This is a picture of the barbs — there scales look to be coming off?

 

I would continue with the water changes although I feel like if there was that bad of a smell you should be able to find the cause... maybe something decaying? Although you said you found nothing. Is there flow that could move all the decaying food and poop into one non-accessible spot? Just throwing ideas.

 

I removed all the decor and found some floating food but I removed it with the siphon. Should I clean the fx6 again even though I just did it last week? Maybe it has something in it??

 

I dont think it would hurt to check.

 

Could the barbs having some sort of disease that could cause the smell? I heard something about corydora secreting some sort of toxin when stressed and they had total tank loss? .. idk how true that is but I’m grasping at straws here. I just checked the fx6 and it was smelly(obviously) but nothing abnormal.. I even changed out the floss just in case…

 

I have no idea. I think its just a waiting game now. Unless its like a huge thing rn where its in the middle of your room and your entire house smells because of it I would wait and see if it goes away. It seems like you did all you can for now. Maybe someone else has an idea. Sorry I couldnt be more help.

 

I appreciated all the help from everyone!!! I’ll keep y’all updated… fingers crossed it’ll go away soon.

 

I got to thinking last night — what if this is a bacterial bloom? The water this morning if white cloudy and still has that smell() but if it’s a bacterial bloom — it kinda explains the sudden onset, the cloudy water, the smell ‍. Thoughts?

 

I'm gonna go out on a limb here and suggest you clean out your inlet and outflow pipes in the tank a lot of times these items are missed on routine cleaning maintenence and they pick up all kinds of stuff as it delivers it to the filter.
My guess here is that you didn't clean your intake connector and there's a nice layer of gunk stinking up the water. Outflow would be mostly the outside of it because the filter is catching stuff.

I could be wrong. No idea what else it could be if not that. Just taking a guess. Are you sure your filters are working right? I know my tanks get funky when the flow is wrong.

 

I'm gonna go out on a limb here and suggest you clean out your inlet and outflow pipes in the tank a lot of times these items are missed on routine cleaning maintenence and they pick up all kinds of stuff as it delivers it to the filter.
My guess here is that you didn't clean your intake connector and there's a nice layer of gunk stinking up the water. Outflow would be mostly the outside of it because the filter is catching stuff.

I could be wrong. No idea what else it could be if not that. Just taking a guess. Are you sure your filters are working right? I know my tanks get funky when the flow is wrong.

I checked all pipes and do usually at least every other month. The next morning I found that the water is white cloudy so I contacted a local fish aquarium maintenance company and they said it was a bacterial bloom. So I started to add the beneficial bacteria in the morning and by the afternoon all the fish (except the green terror) were doing great and the water was cleaning up. This morning however when I checked the levels- ammonia was up to 0.25ppm so I did a small 25% water change.

 

I changed my fx6 filter last week during the water change and then the eheim I did today. I use chemipure, carbon and zeolite.. nothing has changed with those. All fish are accounted for. Nothing in the substrate. I cleaned the rocks and put them back in. I’m going to trash the plastic plants because they smell horrible.
I just don’t know what it could be… should I do another 25% water change tomorrow and daily until the smell goes away?

Did you throw away all the old filter media?