What was pH level? and what kind of fish do you have? Most community freshwater fish will be comfortable at 6.8-7.8. There are exceptions of course and if you plan on breeding sometimes parameters have to be closer to optimum for a specific species.Do you have well water?Also, if you have bubble bars,airstones, and any thing that agitates the water surface rapidly, sea shells, certain rocks,stones and gravel(some aquarium gravel is marked non pH altering but it does), ceramic decorations, most sand substrate, and then some all can contribute to high pH. It has been said sudden changes can be deadly but I think that is when other water conditions are of concern (Ammonia, nitrite etc.).I have dropped my pH from 7.8 to 6.5 in less than an hour when getting use to a CO2 injection for my plants. One or two fish got a little lathargic for a minute or two but recovered quickly. In my experiences products like pH down and the like dont have long lasting effects if they work at all. The pH may go down a point or 2 but then will rise just as quick. It becomes a battle of constant additives and fluctuation that is more deadly than a sudden alteration. The only things that lower pH effectively that I have used is CO2 injection (being the best but a little costly but for a 20 gal. a DIY yeast system will work fine), peat moss (The only problem is it makes the water a little brownish) and reverse osmosis water (A RO system is costly and you have to add trace elements back to the water adding to cost and maintainance). I have never tried seachems "pH down buffer" but it is supposed to turn carbonate into carbonic acid(CO2) and lowering your pH.Any way if you have a pH and don't want to fuss with altering it there are neat fish that love higher levels. African cichlids, brackish water fish, and even salt water are all very colorful and prefer a high pH.

I have a PH off the chart. It is also a 135 gallon tank. When I had my first tank a 30 gallon, I bought everything under the sun to keep it down. I worked at a pet store and that was what I was being told. But when I did a water change it went right back up because we have such hard well water in our city.

After I quit the pet store A friend of mine who sold pets
helped me get my 135 gallon. I do nothing with the PH. I do my water changes add novaqua, a little aquarisol incase
eo prevert ick. and that is it.
When I went to houston wholesalers I learned alot. Except
for declorinating the water all the pipes they have coming
in an there were alot going to fish tanks, Massive pipes.
They came straight from the city water line. It was facinating what I learned from them.

I have silver dollars, bala sharks, 22 inch irridecent shark, a 7 in. irridecent shark, a clown loach, a gold tin foil barb and a silver tin foil barb. I also have 1pleco
that is about 12 inches long and one 4 inches long.

The greatest difference with high PH is if you have a little ammonia, The high PH intensifies it. And since excess food turns into ammonia, Fish waste is ammonia.
It is very important to do your water changes. The more fish or the smaller the tank, the more water changes.

Also to add fish to my tank where I know the fish store is
at 7. PH I will float the fish to get his water the same
temp. Them I will pour him in a very clean bucket I have some very fine airline tubing, Smaller than regular size, And I will syphon water from the tank to the bucket. Just till it is almost three times the amount he came in. This brings the PH of the water he is in up to the PH of my tank.
I will catch him in a net and put him in the tank. I never put anyone elses water in my tank.

This is just what I do. I know some fish like the PH lower to breed. But I am not interested in breeding fish.

Sandy

thanks for advice. we are looking into adding the nutrafin co2 system to that tank. we also have a 29 gallon tank and the ph in that tank was fine. we are on town well water and we do frequent water changes we are not interested in breeding

I think that something in the tank must be leeching into the watersince you have no problems with the other tank. It could be gravel, rocks or a decoration of some sort. Also, is there alot of surface agitation (airstones or bio wheel filter)in the 20 compared to the 29 gal. Sometimes well water can test lower pH out of the tap because it has alot of CO2 in it. When the water is aerated it causes the CO2 to release and will make the pH rise.I would try to find the reason for the difference before adding CO2.

we added 2 small seashells to the tank could that have raised the ph thanks jeff

Seashells will raise pH. They are Calcium Carbonate. Avoid these and gravel/rock/sand made of this. This includes limestone and most gravels marketed for saltwater. Make sure you haven't added anything else of this nature to the tank beyond the seashells too.

If I were in your position, I'd remove the seashells and start doing water changes until the pH comes back down. Say about 25% every few days until the pH drops to reasonable levels.

Don't play with CO2 unless you are keeping live plants. There is really no reason to other than for plants. I would *never* use ph up or ph down solutions.

Absolutely the seashells. If you like the look you can find epoxy coated ones that are safe and wont leech the calcium carbonate.

Seashells are only suited for freswater use in tanks with fish that prefer highly alkaline and hard water like Malawi and Tanganyka cichlids.

thanks all we removed sea shells and will be doing a water change