Why can’t I raise the hardness of this tank?
In November last year, I swapped out my well-established 180-litre community tank for discus. It runs two external Ocellaris canister filters and ammonia and nitrites have always been zero, with a trace of nitrate and 7-7.5pH.
I did extensive research in preparation for the discus. As advised, I swapped out the gravel substrate for sand, did a 50% water change and increased the temperature. The day before adding the fish I had the water tested at the shop and was assured everything was perfect. I routinely tested the water for several weeks after adding three discus and everything appeared to be stable to the point where I was advised I could add three more, which I did.
But over the past few weeks the pH has dropped, resulting in filter failure and an ammonia spike. I did daily water changes, dosed with Prime and Stability and tried to bring the pH back up with a discus buffer. I fed the fish minimally and to be honest they appeared to be weathering the storm —no outward signs of stress, and they were eating and active.
But after two weeks there had been no change, and when I tested the hardness of the water, it was so soft that it wasn’t even on the chart. I added two pieces of ocean rock, as advised by my local shop, in an attempt to raise the pH and keep it up, but I’m still having to buffer every other day.
I purchased some Seachem Equilibrium but there hasn’t been any change so far in hardness or pH—and I still have a constant low level of ammonia. How long will it take for levels to rise and am I doing anything wrong or missing something completely?
I have a smaller aquarium with community fish and both tanks have always been identical in their readings until now. The only difference is that the smaller tank has gravel. I carry out weekly 40% water changes on both tanks.
CAROL THACKRAY
JEREMY ADVISES:
I’m sorry to hear you are having problems with pH, KH, and ammonia with your discus tank, but rest assured I have experienced exactly the same thing. For decades I kept fish in the East
Midlands with no problems because the water was hard and every time I did a water change I got all the pH and KH buffering I needed. When I moved to the north west of the country however, I found that the tapwater can frequently have a KH (carbonate hardness) of zero, despite having quite a high GH (general hardness). Those who crave soft, acidic water may see that as a blessing, but
I’ve experienced pH crash on all sorts of situations from koi ponds to discus tanks, and when working as far apart as Southport, Wigan, and Stockport.
Just like you, when the KH I was adding was at zero, pH began to plummet in my discus tank, and water changes actually made it worse. Test kits revealed a pH of 4, the biological filter ceased to function, and the ammonia then began to register. Even adding crushed shell didn’t help.
The good news is that, at very low pH, ammonia is not toxic, although conversely, if you had increased that pH rapidly, the ammonia would have become toxic, leading to an even worse situation.
It sounds like you’ve already tried many of the fixes I would advise. Add discus buffer to the water change water, and if it isn’t working, add twice the amount. The more bicarbonate you add, the more buffering will occur and at some point, it should start to make a difference. It doesn’t have to be discus buffer either—have you tried a pH buffer like Proper pH, which claims to hit a pH value of your choice and hold it there, for example?
My advice is to stop changing the water. You need to get the biological filter back up and running. Stop adding bottled bacteria—there was enough there before, and it’s still there now; it just can’t do its job due to the environmental conditions. Prime detoxifies ammonia, even at normal pH levels, so dose the whole tank once before you start to raise the pH. Changing water will only stall the rematuration of the tank, and further dilute its buffering capacity.
Instead, I recommend that you invest in a digital pH monitor like one from Milwaukee, or better still, a Seneye which will test pH and ammonia throughout the days, show the trends, and even alert you.
Use a measuring jug and a pH buffer powder and add very small amounts throughout the day. A monitor should then show a slow rise and return of pH and with that the biological filter should restart. This may take a week, but that’s a good thing because you don’t want that ammonia to suddenly become toxic. Adding buffer may become a daily task, but you could even invest in an auto-doser to add that buffer for you. Always buffer water change water to the KH and pH you need before it goes into the tank, and only change the water if nitrates are rising above 40ppm. This is one instance where a straight water change is clearly not helping.