FishProfiles.com Message Forums

I have already posted his issue in the past. My tap water is roughly around 6.8 but for some reason something in my tank raises the pH to about 7.8.

We never worked out the reason however, and I was also wondering after doing a water change yesterday that if I add my normal 6.8pH tap water to my 7.8pH aquarium, will this stress out my fish?

I changed about 1/4 of the water, maybe a little bit less. Can anyone see a problem with this? I was thinking that maybe I should raise the pH of the tap water before i add it to the tank. Is this necessary?

The usual stuff (some of it from the other thread) applies:

1. What's your substrate and decorations? I don't think you ever answered this question in the other thread, but it is crucial to resolving the problem. If you happen to have something that naturally raises the pH (say you picked out that nice crushed-coral substrate at the LFS) then your pH is going to go high pretty much no matter what you do.

2. What's your tapwater's natural pH? When tapwater first comes out of the faucet in some areas, it has dissolved gasses in it. If your tapwater has a lot of dissolved CO2 when it first comes out of the faucet, then when that CO2 comes out of solution and into the air, the water's pH is going to go much higher.

To test these effects, leave a container of tapwater out for a day or two. Test the pH at the beginning and at the end. If the pH stays at 6.8 or something else reasonably low, then you know that the problem is something in the tank. If the pH goes high, up to that 7.8 range, then you know that the problem is that your tapwater is really high-pH water.

On the other thread GaryRoland pointed out that fish don't really need a particular pH as much as people assume they do. This is both because fish are naturally adaptable and because most of our fish came from fish farms where the water properties are likely to be fixed for every part of the farm.

Also remember that many LFSes will keep their fish in the natural tapwater of the region and will rely on acclamation to keep them in good shape. One of my local LFSes uses essentially the same water that I have out of tap (7.6 pH) even if the fish are nominally acidic-water fish.

thanks for the quick informative reply. i'll try leaving some tap water out for a couple of days and test it again.

just to inform you though, in my tank i have the following:
- rocky gravel (i have brown and black coloured gravel. I don't know what the stuff is made out of but its the sort of stuff people use for cactus pots etc...
- 2 x plastic hidey hole decorations MADE for an aquarium with fake plants attached.
- 1 mangrove log
- java fern

Thanks again and I'll post back with the new results!