Random Lowered PH

I've had a tank setup for about 8 months now. It's 360 litres it's got a large 2000litre per hour canister filter filled with over 5 litres matrix media and some other ceramic ring ect not chemical media though. I've been doing a lot of water changes on it practicing for when I get discus for it(it's currently fully stocked with tetras angelfish ect but will be changing ove run a few months once fully established and stable) I've got 7 fish tanks all of the pH's in these tanks are 7.6 and the tap water comes out at 7.6 but in this tank the pH is 6.6 for some reason. The parameters are 0 ammonia 0 Nitite 0-5 nitrate it is fully cycled. There is no driftwood in there atm, some vallisoneria in gravel and rI'm root tabs below the gravel. Root tabs I've tested myself and they make no difference to pH what so ever same with the gravel. I'm really stumped as to why it is lowered. Thanks if anyone has any ideas why.

The temperature is 30 degrees btw

I've got a 360 litre tank that's been set up for 8 months. It's got gravel bottom with vallisineria planted in it. It's got soem root tabs in the gravel. (I've tested both in tank water form different over a few days with no changes what so ever) The pH in this tank is 6.6 however the pH of my other 6 tanks and the tap water is 7.6. The tank parameters are 0 ammonia 0 Nitite 0-5 nitrate and temp of 30 degrees. It's fully cycled and stocked. Been doing 30 percent water change every 2-3 days practicing for discus. Theres no drift wood int he tank or anything so I'm not sure hwy the ph is lower than everything else. Filter is full of matrix ceramic rings and sponges no chemical media what so ever in tank. Thanks in advance hope someone can help.

 

Going to need a little more info. What kind of substrate? How long have the fish been in there? How many tetras and angel fish? How often do you change the water? Is the substrate the same in all tanks? And is the cleaning routine the same?

 

The kH is slowly depleted over time and the pH slowly goes down? That's my best guess.

 

Going to need a little more info. What kind of substrate? How long have the fish been in there? How many tetras and angel fish? How often do you change the water? Is the substrate the same in all tanks? And is the cleaning routine the same?

The substrate is inert gravel used in multiple tanks same with the root tabs. There's 1 angelfish and quite a few tetras and other fish. Nitrates are always low any way but I've been doing a lot of 30% water changes lately to see if they can easily be kept under 5 for some discus in the future which is easy at current stocking level.ill be swapping the fish over not getting more.

The kH is slowly depleted over time and the pH slowly goes down? That's my best guess.

Surely though the tanks that's I've had set up for over a year and with lots more fish and plants and with a lot less water changes ect haven't budged a bit all this time? I really don't get why it's down. Thanks you though going to buy a gh and kh kit anyway soon

 

Ok still something must be different. I was thinking lack of water changes. Sometimes that does lower the ph. On the bright side a ph of 6.6 is great for discus and angels and tetras.

 

Ok still something must be different. I was thinking lack of water changes. Sometimes that does lower the ph. On the bright side a ph of 6.6 is great for discus and angels and tetras.

Thanks I know it would be better for discus at 6.6 but I'm worried that if I do frequent water changes and larger than 30% water changes it will stress them as the tap water is 7.6. Thanks though.

 

With all your water changes is the ph changing?? Don’t worry about nitrates they really don’t matter. It’s long time (months) exposure that will hurt fish. And over 40ppm. Most will recommend a water change when nitrates hit 40ppm. I change water every 2-3 days on my discus tank weekly on the rest.

 

With all your water changes is the ph changing?? Don’t worry about nitrates they really don’t matter. It’s long time (months) exposure that will hurt fish. And over 40ppm. Most will recommend a water change when nitrates hit 40ppm. I change water every 2-3 days on my discus tank weekly on the rest.

No goes up a few point something then by the morning it's back at 6.4 or 6.6 I'm doing it 2 or 3 time a week because I want to keep discus in there eventually and want to see what it takes