Ammonia Rise From What?

[Winterlily]

I've got a row of three 5.5 gallon tanks, each housing a single male betta. All are fully cycled and have been showing 0 ammonia and 0 nitrite for quite a while now. All are fairly heavily planted with live plants. I'm having an algae issue in these particular 3 tanks, so Saturday I added 1 Amano shrimp and 2 nerite snails to each tank. One of the tanks is still 0/0 and I can locate both snails and the (very bold-acting!) shrimp. The second tank is still 0/0 and I can locate both snails but not the shrimp. The 3rd tank is a problem suddenly. I'm getting a reading of 0.25 ammonia and somewhere just under 0.25 nitrite (but definitely not 0). I can locate both snails but not the shrimp. I just did a small water change in that tank and purposely stirred up as much as I could with my hand to see if I could see him scuttle somewhere - nope.

So. Do I have an issue here of that the shrimp died somewhere and is decaying, causing the ammonia to rise? Or is just the addition of the 1 shrimp and 2 smallish snails enough to do it? If it's the additions, why isn't the ammonia rising in the other 2 tanks too?

 

[aly_starh]

it might be left over food, waste etc on the substrate that has not been cleaned up.


~betta_246

 

[Winterlily]

Well yeah, I suppose it could be, but the tanks are vac'ed and 30% water changed every week, and I've never (beyond the intial cycle) had an ammonia or nitrite issue before. The other tanks, with the same amount of fish and plants, and fed the same, don't have any issues either.