I have a freshwater 75 gallon that has been set-up for well over two years. In the past 6 months, I have had this persistent low level ammonia reading, between .25 and .50 PPM
. I use the API Freshwater Master Test Kit, which is about a year old now.
I have two filters going. One is a large sponge with a Hagen (can't remember the actual model) 70 powerhead in one corner, and an AquaClear 110 in the other. Media is stable; I rinse both sponges (in water removed from the tank) and replace the carbon and ammonia removal media once a month. I do 25% water changes weekly.
I am getting, as I said, Ammonia readings at .25 and .50, Nitrites are 0, Nitrates are reading 0 - 20. (Dechlorinated tap water tests 0 for Ammonia). pH in tank is reading 7.8, which is also what the dechlorinated water straight out of the tap tests out at; temp is more or less steady between 74 and 76. Just for test purposes, I did a full 50% water change on Tuesday and the ammonia level didn't change as of Wednesday's (22 July) or this morning's (24 July) reading.
The tank has two small clusters of live plants and the rest are artificial. My current inhabitants are two white clouds and two Cories, all four of which are active and healthy. I know I am not overfeeding; I feed sparingly anyway. I use the Sanfrancisco Bay Brand Freshwater frozen multipack; each cube lasts me a full week.
I want to add Swords, Mollies and a few Platies, however, I am hesitant with the consistent Ammonia readings.
Any ideas? The thought HAS crossed my mind that the Ammonia test reagents might be the culprits but the 0 Ammonia reading on the tap water sort of blows that idea out of the water..so to speak.