Question about water changes and pH

[jlbfish]

I have 7.4 pH straight out of the tap. My tanks vary from 7.4 to 8.2.

If i do 50% water changes 1x per week would the 7.4 be dangerous for the fish in the 8.0 and 8.2?

All of my fish seem fine for a while BUT I have had a problem with wild caught Corydoras Hasbrosus and this may be it.

My tanks are as follows:

Straight out of tap: 7.4
24hrs out of tap and aerated: Not sure yet
5 gallon with betta pH 8.0
20 gallon ISO with 8.0 3 Bosemani Rainbows and 1 Australian Rainbow 8.0
28 gallon (6 C. Hasbrosus, 6 Neon Tetras and 4 Threadfin Rainbows)
75 gallon (4 False Julii Cories, 6 Peppered Cories, 10 Flame Tetras, 10 Red Eye Tetras) 7.4

Clearly for the 75 gallon all is good. My Betta tank and 28 gallon are due for a water change the 28 gallon needs one. The water parameters are all fine 0 Ammonia and Nitrite and 5-10 Nitrate. I just don't want to pH shock any fish. I've lost 5 C. Hasbrosus so far

Make that 6. Maybe it is high pH in general and they are wild caught. Maybe the LFS will take them back. Anyway I did switch out 5 gallons in the 28 gallon yesterday since it is due for a water change. I seem to lost them around water changes :/

 

[Daxhua]

Have you tried using peat moss or driftwood so that it gradually lowers your ph overtime?

 

[jlbfish]

Not yet. I am going to try Indian Almond Leaves thanks to Rivercats suggestion. I may try Pete and/or more driftwood over time. I'm mostly concerned about water changes and if they can cause a problem.

Thanks!

 

[My toddlers tank]

I would add driftwood, maybe try smaller water changes a couple of times of week instead of 1 big one that way the change in the ph won't be as big.

 

[Daxhua]

Not yet. I am going to try Indian Almond Leaves thanks to Rivercats suggestion. I may try Pete and/or more driftwood over time. I'm mostly concerned about water changes and if they can cause a problem.

Thanks!

I've heard that they can on smaller tanks like yours so maybe smaller water changes or a 50% every two weeks.

 

[My toddlers tank]

Using Indian almond leaves in aquariums

This is a site I found on the leaves