What causes swings in ph?

[Azrael]

What cause swings in ph? My ph has always stayed about 7 and the last few days I've noticed my arowana and bichirs haven't been very interested in eating. Tested the tank everything is fine nitrates are 10-15 temp is kept at 78 but my ph went down to 6.6. The tank is a 240 with a 2gph drip. Ordered a bag of crushed coral that will be here in a few days also purchased an Apex neptune Jr, still need to calibrate my ph probe but it will be nice to have my ph monitored. I had a bottle of api proper ph 7 so I added that last night

I've read that ph swings can happen from overfeeding? But if that was the case wouldn't you be getting ammonia spikes? Anyways any feedback would be appreciated.

 

[FJB]

Unfortunately, I don’t know what is the cause of the pH changes you are observing.
But I wanted to comment on your tank(s). Beautiful long stands. Beautiful driftwood; is that real? If not, very realistic.What kind of lights are those 3 in the main tank?

 

[fishdance]

Plenty of info online about carbonate hardness to buffer /preventing pH swings.

One thing often missed is that low pH can crash your biological filtration producing ammonia spikes which are rendered safe below pH7 but may burn your fish once your pH returns.

 

[Azrael]

Oh thanks, yea the whole thing was alot of work lol. Driftwoods are fake from universal rocks as is the rock background. The lights are Kessel A360X, they are actually a salt water light but I loved the aesthetics of the light I opted for those over the freshwater version . Thanks again for the kind words.

 

[Azrael]

Plenty of info online about carbonate hardness to buffer /preventing pH swings.

One thing often missed is that low pH can crash your biological filtration producing ammonia spikes which are rendered safe below pH7 but may burn your fish once your pH returns.

OK thank you I guess I need to do more reading

 

[duanes]

Fish are constantly putting out carbon dioxide, and other acids in their waste. Both decrease pH.
When younger, the volume of water in the tank, and its buffering capacity could probably easily hold pH steady.
I would imagine they have grown quite a bit as time went along, and the buffering capacity, with a normal routine may not now, be as adequate at buffering, as it was when they were smaller.
A drop from 7 to 6.6 is not that drastic but may be an indication that water change volume, and frequency of the water change may need to be increased, to accommodate the fish, that are now much larger and their CO2 and uric acid output has increased.
It may be necessary to double or triple the drip.
To accomplish this with my waters normal buffering capacity (calcium hardness of around 100ppm), it is necessary to change 100% of my tanks water per week.
So with that routine the tanks pH holds steadyat 8.2, and nitrate remains at no higher than 5 ppm.
Although because I use heavily planted sumps, pH may be 8 or drop to 7.8 in the morning after the plants have been using oxygen at night, fluctuating back to 8.2 late afternoon after a day of the plants using CO2 and producing oxygen.

 

[Azrael]

Fish are constantly putting out carbon dioxide, and other acids in their waste. Both decrease pH.
When younger, the volume of water in the tank, and its buffering capacity could probably easily hold pH steady.
I would imagine they have grown quite a bit as time went along, and the buffering capacity, with a normal routine may not now, be as adequate at buffering, as it was when they were smaller.
A drop from 7 to 6.6 is not that drastic but may be an indication that water change volume, and frequency of the water change may need to be increased, to accommodate the fish, that are now much larger and their CO2 and uric acid output has increased.
It may be necessary to double or triple the drip.
To accomplish this with my waters normal buffering capacity (calcium hardness of around 100ppm), it is necessary to change 100% of my tanks water per week.
So with that routine the tanks pH holds steadyat 8.2, and nitrate remains at no higher than 5 ppm.
Although because I use heavily planted sumps, pH may be 8 or drop to 7.8 in the morning after the plants have been using oxygen at night, fluctuating back to 8.2 late afternoon after a day of the plants using CO2 and producing oxygen.

Thank you for the explanation that makes alot sense. So it's on a 2gph currently, tank is 240 with 40g sump. So I'm already doing like 120% change a week. Should I maybe throw a 5gph dripper instead?