Bacteria keeps dying. Help/Advice

Background info I cycled the empty 23 gallon tank for a month before seeing Nitrates and added fish gradually. 10 Cherry shrimp, 13 neone tetras, one Beta and two Sword tails. I feed the fish twice a day. AMOSIJOY 172GPH Canister Filter, with a floss pad, carbon sponge, ceramic filter rings, and Bio balls.

My problem is that my bacteria seems to die every 2 weeks or so. I see my Nitrates fall to zero, then the ammonia starts to go up slowly. I was told that maybe my filter is doing too good of a job and starving the bacteria. Is that possible? I keep having to add bacteria to the tank and I am wondering if I should just add more fish to creat more waist. I think the ammonia spike caused the beta to get a touch of fin rot, I am currently treating him for it and he is doing well. Adding the Nitrate/Nitrite readings for this tank (left) and a shrimp tank (right)

TLDR: Bacteria dies off (I think it's being starved), should I add more bio load or change the filter to something else. Also, is there something that may be killing the bacteria?

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u/EphemeralAttention 8h ago

What are your KH and PH levels like? Nitrifying bacteria use carbonates as their primary carbon source, so if your KH is dropping to zero that can cause the cycle to stall. The bacteria also work best at pH levels between 7-8. They still process waste between 6-7, but if your PH drops below 6 the cycle will significantly slow down.

Edit: fixed typos

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u/falcon_311 7h ago

I didn't know nitrifying bacteria use carbonates like that. All of my tanks run at 0kh so I guess my bacteria is living on hopes and dreams lol.

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u/Azedenkae PhD in Microbiology 7h ago

The thing is once the nitrifier population is established, their consumption of ammonia/nitrite is for energy, not for growth. So they no longer really need that much carbonate once the cycle is done.

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u/falcon_311 7h ago

Oh, that's cool