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Discussion Starter · #1 ·
Not the same as regular "old tank syndrome" because there isn't a problem with nitrates. But the problem that shrimp haven't bred for a long time now, and babies don't survive. The tank is 1.5 years old, and the first half year or so, the shrimp were lively every day, but now there are periods of "good days" and "bad days" where the shrimp just tend to stand around. Initial pH was around 6.0 but now is in the upper 6's. Did the substrate "run out", or is there an accumulation of toxins and other bad stuff? The water change schedule is about 15% every week. How to fix this?

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The last "good streak" was about a month ago, while a large Indian Almond Leaf was breaking down and the shrimp would eat at it every day. Eventually a lot of poop piled up, the nitrates started to rise, and that's when the "bad days" started. Despite gravel vac, dosing no ferts, and the water changes, (nitrates back to zero) the tank still hasn't really recovered from this.

BTW, the substrate is UNS controsoil. On the other hand, I have another tank that is even older with this substrate, rather neglected with a big overgrown moss wad in the center, and the shrimp in that one seem to be doing ok.
 

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Changing the substrate might be the answer. I've heard of shrimp doing this once the substrate starts to exhaust itself and the pH rises. Once it's refreshed, they come back alive!


As for the other tank, what's in it? What's the pH? Substrate?
 

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Discussion Starter · #5 · (Edited)
Once I cut back on the ferts, the S. repens starts to yellow and lose leaves. The ludwigia has been slow to grow recently. Similarly, the peacock moss seems to branch less when some kind of nutrient is low, and more when nutrients are high. Or maybe it is lighting, I dunno.

I'm thinking that the most gentle way to change substrate is to replace one section at a time. Also to pre-soak the new substrate because even UNS controsoil releases a small amount of ammonia. (The directions say do not rinse, but I assume that only applies to a new tank that hasn't been cycled yet)

The "other tank" also has UNS controsoil, but brown color instead of black. The ph was also mid-upper 6's last I checked a year ago. I haven't checked the water parameters in that tank in a really long time. It was going to be my "neglected tank", but the few shrimp in it seem to be doing well. (two Amanos and two Tainwan Bee only)

Another idea: Maybe it's time to clean out the HMF filter? I thought they were supposed to run for a really long time.
 

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Does sound like your substrate needs refreshing. I'd clean up the filter to rule out malfunction (rinsing media in water change water and clean out hoses and inlet/ output) but I do think it's just your substrate being used up. Sounds like you have a handle on that 😉👍
 

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Discussion Starter · #7 ·
Just an update to say that I changed most of the exposed substrate. The other substrate is under a carpet so I can't change it. The UNS controsoil in a jar with remineralized RO water reads ph of 6.0, but even after this substrate replacement the pH is still 6.6 in the main tank. So I think something is buffering the pH up. The tank is still not back to normal, though. Algae has started to grow, but the indian almond leaves aren't breaking down, and the shrimp are still kind of "quiet". Maybe something is off with the bacterial balance or whatever. Perhaps also a good time to clean out the HMF filter?
 
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