Air driven sponge filters and pH

I use RO water remineralised to pH 6.5
In my display tanks and other tanks that have cannister filters i have no problem with this.
I am intending to set up a rack of breeding tanks and in an attempt to save on electricity bills etc i am going to use air driven sponge filters. The idea being that i can run a number of tanks from one air pump and only use the same electricity as one cannister filter.

I have begun aging and cycling some sponge filters in one of the tanks that is mainly filtered by a cannister filter.

My problem is that when i turn on the air pump to pull the water through the sponge filter the water disturbance immediately causes the pH to start rising.
I understand the process, and any disturbance of this kind, particularly when bubbling air through the water column will cause an increase in pH.

So what do you do ?
The tank in which i have begun aging a sponge filter has risen from pH6.5 to pH7, higher that i want for my Angels, discus or my Dwarf cichlids, and it looks like it is going to go higher still.

Any suggestions ?

Any advice or guidance gratefully received.

Thanks
gibbo

Turn the air flow to the filter down, what matters is the flow of water through the sponge, a lower rate of bubbles might actually result in more water flow. Position the outlet from the filter as close to the surface as possible so that there is as little disturbance on the surface as possible. If this doesn't work, remineralise the RO to a lower kH, but, unless you're breeding wild fish, a ph of 7.0 is fine for the angels.
For the dwarf cichlids use some bog wood in the tank (you can do this for the angels & discus too). not only does it slowly leach tanins which are acidic, as it slowly decomposes it helps to add CO2 to the water which will increase the acidity.

Thanks again.

As usual the answer will probably be a combination of all of those suggestions.

I am even considering un-planting my display tank so that i don't use CO2 injection on that one, then i might be able to return to all of my tanks having the same water parameters.



cheers



g