Shrimp tank woes/old tank syndrome/chlorine readings
I have an established 20 gal tank of 3 years that I converted into a shrimp only tank for my neocaridina shrimp about 2 months ago. I also have one bristlenose pleco and a mystery snail.
In the past two months, I have added live plants such as hornwort, Christmas moss, Java fern and Anubia.
I have inert substrate
My water parameters are currently as follows:
72 degrees
GH 8
Nitrite 0
Nitrate 25
Chlorine 0.8-1.5 (without prime)
KH 4
pH 7
TDS 415
I have very hard well-water, so I use an RO unit that I remineralize with Shrimp mineral GH/KH+. I’ve been slowly trying to remove 5% water 2-3x a week and replenishing with new water.
About a month ago, I started noticing KH and pH drops. I added a small bag of crushed coral to my HOB filter. I also should add that I added a sponge filter for extra filtration and oxygen. I started to notice that I would get chlorine readings on my test strips almost every morning or every other morning. I would dose the tank with prime and it would register as 0. I don’t understand the chemistry enough as to why chlorine would show up in my tank as I do not add any untreated water. Could it be the crushed coral? Is it old tank syndrome combined with crushed coral? I have removed the bag of crushed coral in the meantime.
I have lost several shrimp in the past two months, but currently the shrimp have been doing well - several berried and I see shrimplets, and my mystery snail had laid many clutches, but the chlorine readings worry me and I end up dosing prime directly into the tank whenever I notice it. But, if I’m not in town for a period of time over a few days, I’m worried that the chlorine levels will rise and I will come back to the entire colony being wiped out.
thanks in advance for any insight