Why does the cycle on my 10 gal platy tank keep crashing?

Hi, my 10 gal tank with 5 adult platys and 1 surviving juvenile appears to repeatedly crash (cycle).
Parameter history ( recent, but seems repetative):
4/5/21
PH- 7.4
Amm- o.25
Nitri- 0
Nitra- 5.0
Action- added Prime only

4/6/21
pH- 7.4 (stable)
Amm- 0-0.25
Nitri- 0
Nitra- 40-80
Action- 30% h2o change, added stress coat & aquarium salt

4/7/21
pH- 7.4 (will remain at 7.4 unless otherwise stated)
Amm- 0-0.25
Nitri-0
Nitra- 5.0
Action- Prime

4/8/21
Amm- 0-0.25
Nitri- 0
Nitra- <5
Action- Prime

4/9/21
Amm- 0-0.25
Nitri- 0
Nitra- 0-0.5
Action- Prime

I have tested for ammonia in my tap water, which clearly tests 0. Why do I continue to show some ammonia in the tank, and loose 99% of the measurable nitrates?

 

How long have you had the tank running? .25 ammonia may mean your bb can’t keep up with the load. What type and size filter are you using. Nitrates disappearing is strange. How often do you clean your filter?

 

IMO there is no reason for excess prime at 0.25ppm ammonia. Let it run it's course at that level. The results you post seem to be from stips instead of liquid due to the flux in nitrates and tiny amounts of ammonia. Good luck.

 

I added 5 Platys after cycling this 10 gal for 8 weeks (this was in January 2021). I tested daily for almost a week before adding fish to be sure I had a solid cycle, which I did... 0 ammon, 0 nitri, measurable nitra's. I never clean the filter, it is the disgusting looking mess that it has been since cycling. It is a hang on back filter that came with the tank kit. I also added a corner sponge filter. Additionally, I run an airstone for plenty of water movement and O2. The fish appear happily active, and in no distress.

 

How long has the corner filter been running without cleaning? I would rinse out the filter media in your hob filter the next time you change water. Clean the media in the removed water. Than return that media back into the hob. The following week I would clean the corner filter. Clean them on opposite weeks and go 2 weeks in between cleanings. It could be that your hob is eating the nitrates because it’s so dirty and the flow is probably much slower than when you first started it.

 

How long has the corner filter been running without cleaning? I would rinse out the filter media in your hob filter the next time you change water. Clean the media in the removed water. Than return that media back into the hob. The following week I would clean the corner filter. Clean them on opposite weeks and go 2 weeks in between cleanings. It could be that your hob is eating the nitrates because it’s so dirty and the flow is probably much slower than when you first started it.

Thanks, I will give it a try.

 

I might be wrong but I see your nitrates going down after a water change, which is perfectly normal.

The next days nitrates stay at 5 ppm, which is good. I don’t see a problem with nitrates but ammonia is and you’ve had good advice on that.

Adding 5 fish at a time was probably too much and your BB couldn't handle it, thus the slight ammonia spike.

 

Salt was added? Salt will kill some nitrifying bacteria and cause different strains to develop that are more adapted to the increased salinity. The result is a temporary ammonia spike while the colony adapts...