had a well established tank, changed gravel and decorations, nitrites high

hello new to these forums made this account for this question. I'm fairly new to aquariums as ive never had one myself but I did work at a pet store for a few years and have helped others with theirs so felt fairly confident in my abilities to run the 10 gallon tank that was gifted to me. came with all the proper chems, rocks, plants, and food. set up the tank added the nitrifying bacteria waited a few days and then bought 4 fish when water was reading fairly normal levels (begginer mistake I added all 4 at once) tank went through some pretty aggressive changes but I got everything running smooth within a week or two with no fish loss. well the rocks that were in the tank were a truly horrible pink purple and bright banana yellow color. not exactly what I had in mind so I went and bought more natural stones. from the petstore. I thought I did everything correctly, thoroughly cleaned the rocks and the new decoration. I even left a few of the old rocks on the bottom of the tank to kind of inoculate the new ones (wasn't sure if that would work but was thinking of mushroom farming and colonizing fungI or bacteria). everything seemed fine for a few days so I added a few live plants on the 3 or 4th day after the substrate change. the next morning the water levels went insane, nitrites didnt even have a color deep enough on the charts. I quickly lost my dalmation molly and the others were obviously tressed so I did a big water change and started testing and stressing. now I'm sure that the abnormal levels were part of the nitrodgen cycle and the new bacteria getting established so I took the steps found on the forums here, water changes daily, lower feeding, added some stresscoat and some of the startzyme stuff I got from the pet store (pretty much treating it as a new tank at this point.) ive gotten most of the other levels under control but the nitrites are still through the roof (well over 10ppm) and no matter what I do I can't get it under control. water is extremely cloudy and while the fish seem to be holding on they are obviously stressed. any help would be appreciated and I apologize for the rambling post.

edit: tthe tank was setup for about 2 months before I changed the gravel and its been about 2 weeks since I changed it

 

A part of the old gravel that you left in your tank when you added the new gravel was a very good idea. The bacteria from the old gravel will spread to the new gravel and after 2 weeks (which have passed) you can take the old gravel out if you want.
Sorry, but did you mean Nitrates are 10ppm? You can easily confuse them. Here's how it goes, just in case: Ammonia -> Nitrites -> Nitrates. Ammonia should always be 0; nitrites should always be 0 and nitrates should be 40ppm or lower. I you meant nitrites are 10ppm, then that's way too high! What are your nitrates readings?
It could be possible that your tap water already includes high level of nitrites. It could be a sudden change in tap water parameters. Can you take readings of tap water parameters, too?
Oh, and do you gravel vacuum the aquarium?

 

Welcome to the forum

Do you know the nitrogen cycle? I would click on the blue words to get a better understanding of it.

The molly is definitely not suitable for a 10 gallon and is contributing to your high nitrites. What test kit are you using and what are your current parameters of pH, temp, ammonia, nitrite, nitrates? I would be doing larger water changes to get those levels down. At least 50% back to back.

What are the other fish in the 10g? Also, letting the tank run for a few days with just a bacteria supplement doesn't cycle your tank. You would have needed an ammonia source in the form of fish food, fish waste or liquid ammonia. If you didn't add any of those at the same time as the bacteria supplement, your tank wasn't cycled and ready for fish. I'd pick up a good water conditioner like Seachem Prime which detoxifies ammonia and nitrite of up to 1ppm for 24 hours as well as a good bacteria supplement like Tetra SafeStart Plus or Seachem Stability.

I'd also rehome the molly and the other fish (depending on what they are) and choose fish more appropriate for your tank size.

https://www.fishlore.com/aquariumfishforum/threads/stocking-list-for-10-gallons.207629/

 

I have a red dwarf gourami, a ruby red barb, and a albino catfish in there at the moment(molly has been dead a few days now) unfortunatly all I have at the moment for testing is some cheap strips so I am giving a little leeway to the readings. will be picking up a liquid test kit this weekend. I knew I was over the limit with the fish so I upgraded to a 20 g filter to compensate and plan on upgrading to a 30 gallon tank in the next few months and I imagine they will be much happier there.

I do know the basics of the nitrogen cycle mainly due to what I have been reading here and other forums and I'm pretty sure my tank is on the right track to cycling ammonia is reading close to 0 according to these strips but the nitrites are still through the roof. I have been doing pretty aggressive water changes trying to get the levels down and I finally got it to a color that was actually ON the chart but it seemed to level out and won't go any lower. keep in mind too that before I changed the gravel the tank was fine crystal clear water, levels stable for a month atleast. I know I pretty much have to wait out the cycling I'm just worried about the extremely high nitrite level (I just checked it and its slightly under 10ppm) nitrate levels slightly under 10ppm. fish seem to be stable but stressed.

I have not gravel vacd at all with the new gravel as I ve seen quite a few posts of people saying NOT to disturb the gravel with live plants, that it will kill the plants.

 

None of the fish you have are appropriate for a 10 gallon unfortunately. The DG needs at least a 20g, the barbs and catfish are school/shoaling fish and need to be in a group of at least 6+ so the 10 gallon is much too small for them as well. They will likely be even more stressed and water parameters hard to maintain with all of them in there. I would return them to the store until you get that 30g. You could then choose fish more appropriate from that stocking thread I posted.

Test strips are also notoriously inaccurate so I would invest in the API Freshwater Master Test Kit to verify what your true parameters are. Your tap water could also possibly have ammonia, nitrite and nitrates so I would test those as well.

If you haven't done a gravel vac, that could possibly be contributing to your high nitrites so I would do so with your next water change. You can vac with plants by vacuuming around them in just the open areas.

 

I have a red dwarf gourami, a ruby red barb, and a albino catfish in there at the moment(molly has been dead a few days now) unfortunatly all I have at the moment for testing is some cheap strips so I am giving a little leeway to the readings. will be picking up a liquid test kit this weekend. I knew I was over the limit with the fish so I upgraded to a 20 g filter to compensate and plan on upgrading to a 30 gallon tank in the next few months and I imagine they will be much happier there.

I do know the basics of the nitrogen cycle mainly due to what I have been reading here and other forums and I'm pretty sure my tank is on the right track to cycling ammonia is reading close to 0 according to these strips but the nitrites are still through the roof. I have been doing pretty aggressive water changes trying to get the levels down and I finally got it to a color that was actually ON the chart but it seemed to level out and won't go any lower. keep in mind too that before I changed the gravel the tank was fine crystal clear water, levels stable for a month atleast. I know I pretty much have to wait out the cycling I'm just worried about the extremely high nitrite level (I just checked it and its slightly under 10ppm) nitrate levels slightly under 10ppm. fish seem to be stable but stressed.

I have not gravel vacd at all with the new gravel as I ve seen quite a few posts of people saying NOT to disturb the gravel with live plants, that it will kill the plants.

Wait, did you leave the dead molly in the tank or did you remove it? Also, when you gave readings I thought you used liquid kit. Please be aware that test strips are highly inaccurate and what they show as ammonia 0, it's very likely that's not true.
Gravel vaccuming DOES disturb the plant roots. That's why you don't have to insert the vacuum all the way inside the gravel, but instead keep it just above the gravel so that the waste will be sucked up while disturbing a small amount a gravel.

 

Gravel vaccuming DOES disturb the plant roots. That's why you don't have to insert the vacuum all the way inside the gravel, but instead keep it just above the gravel so that the waste will be sucked up while disturbing a small amount a gravel.

As long as you are sticking your vacuum into just the open areas, it should be fine. A lot of debris/detritus fall in between and under the gravel so it is best to stick the siphon in there. It's not like sand where everything sits on top.

 

As long as you are sticking your vacuum into just the open areas, it should be fine. A lot of debris/detritus fall in between and under the gravel so it is best to stick the siphon in there. It's not like sand where everything sits on top.

Well talking about my aquarium I can't stick it anywhere. I'll either exposed my cryptocoryne's roots or make my anacharis float (which is a big pain to make them stay in the gravel again). So what I do I disturb only around 1 cm of gravel and get the waste out.