Ph won't lower in new aquarium?

You need to stop stressing about the pH. 7.6 is perfectly normal, and most fish will be perfectly happy with that. The active ingredient of "pH Down" is Sulphuric acid, same as is used on car batteries. Not sure how pouring battery acid into your tank is supposed to help your fish?

See while you are busy fussing about the pH, you are ignoring the stuff that really matters, the ammonia and the nitrogen cycle. Those things are probably still OK, because the tank is large, and you only have a few fish in there yet. Leave it that way for a few more weeks, and get a full test kit to monitor the nitrogen cycle.

The reason your pH is a bit high is because of natural dissolved minerals in your tap water. These buffer the pH to a slightly higher level than normal. You add some acid, but it's not enough to overcome the buffering. So you add some more, still no change. Eventually you add enough to make a difference, and the pH suddenly drops to 5.5. You then do a water change, and it goes back up to 7.6 again. Repeat until your fish die of pH shock and ammonia poisoning (because you spent all your time fussing with the pH)

Anyway, you don't have any serious problem, and as you say, the fish are doing OK. Just leave things alone and let the tank system settle down and start running smoothly. Then add some more fish.

I use Proper pH 6.5 to bring my pH levels down from 7.4 or so to 6.4, and that has worked well and stayed stable for years. So you might try this. I do have to add in the full tank's amount each water change, though, not just the amount for the percentage of the water change, so it can be a bit expensive. The only thing is that it shouldn't be used in tanks with live plants.

If you do have live plants in your tank, there are some other ways to lower the pH. Using Reverse Osmosis water mixed with tap to get lower pH and hardness is good, and since that can also lower the hardness your pH is less likely to spring back up. Using peat in the filter will lower pH well too, but it can also color your water the color of tea. Driftwood can lower your pH a bit in the same way peat does, by releasing tannins, but tends to taint the water less drastically. Many soft water fish come from water that is acidic because of tannins, so the coloring it adds to the water is very natural to them.

Many pH products will only temporarily bring down the pH, then swing back up. Especially products like pH down. So you have to be careful which you use.

I use Proper pH 6.5 to bring my pH levels down from 7.4 or so to 6.4, and that has worked well and stayed stable for years. So you might try this. I do have to add in the full tank's amount each water change, though, not just the amount for the percentage of the water change, so it can be a bit expensive. The only thing is that it shouldn't be used in tanks with live plants.

If you do have live plants in your tank, there are some other ways to lower the pH. Using Reverse Osmosis water mixed with tap to get lower pH and hardness is good, and since that can also lower the hardness your pH is less likely to spring back up. Using peat in the filter will lower pH well too, but it can also color your water the color of tea. Driftwood can lower your pH a bit in the same way peat does, by releasing tannins, but tends to taint the water less drastically. Many soft water fish come from water that is acidic because of tannins, so the coloring it adds to the water is very natural to them.

Another possibility that will work especially well for a planted tank is to use an acidifying plant substrate to acidify and soften the water, like ADA Amazonia. This will also provide excellent nutrients for rooted plants. The only thing with this is it may leach Ammonia at first, so you might need to presoak it for a bit before using it in the main tank. Also, it can be exhausted in as soon as a year in extremely hard water and alkaline tanks, so you may have to replace it at some point.

Ghapy is right, leave pH alone. The only time you should be concerned about pH is with wild caught fish. Most freshwater fish are farmed and are raised between 6.0-8.0, and will be able to adjust to anything within this range. The main thing about adding fish is to make sure the water is dechlorinated, add about 3 or 4 fish in the beginning, and monitor ammonia for the first 2 weeks, nitrite for the first 6-8 weeks and then nitrate.

If the fish are still alive, the pH is fine. More fish is not going to help. pH changing chemicals are not going to do anything good for the tank.

Tiger barbs will do fine in high pH levels. And corys like a pH around 7, so 7.6 is probably fine. Like I said, if the fish are still alive you'll be fine.

More fish wont lower your PH levels, though your cories need a larger group(If you have gravel you will want to find them a new home since that will eventually kill them, they need sand or something they can sift without hurting their delicate barbels).

Have you tried driftwood? That often will bring PH down and soften the water. Some substrates will soften it naturally....I have sand in my tanks and the PH is 7.3 or so, the one tank I have without sand or gravel has a PH of 7.8....however I also have driftwood in all of my tanks since I keep fish that like the stuff or need it like plecos. =) So driftwood is my best suggestion, though you will want to research it first. You need to treat it first sometimes, depending where you get it or what kind, and some wont lower your PH or hardness.

Please make sure that lower PH is what your fish need though...and honestly it's usually best to do this before you get fish since changes in PH make them very itchy and uncomfortable. Stress is not good for fishies. =)

Most species of tropical fish can adjust to a ph that is slightly outside of there ideal rang. A stable ph of 7.6 will be just fine for the fish you have. You dont want to add those chemicals to the water to change it, becuase you will end up with bouncing ph, which can kill your fish.

Try to avoid fish that really need a more specific ph. Most tetras ae fine, but cardinal tetras likely would not be. check sites like liveaquaria.com, http://badmanstropicalfish.com/profile.html, before you get any species of fish, any fish that says 6.5 is ideal would be best to avoid.

Now the other thing. Many petstores will have have a much different ph then you. The place I shop at most has a water sofener and a ph of 6.8 , So i have to take extra care to slowly acclimate them to my ph, which like you is 7.6.

http://www.fishlore.com/acclimating-tropicalfish.h...

PH products are bad to use because they can cause your PH to crash and kill your fish. It's much better to just keep fish that are appropriate for the ph you have. A higher but stable ph is better than one that fluctuates. You can use driftwood or peat to naturally lower your ph.

From asker: I'm hoping to add other fish such as tetras and other fish that like a slighty lower ph

You have a buffering problem the water where you live must be extremely hard, you need "drinking water" which has gone thru reverse osmosis and is 7.0, and then you can manipulate it accordingly. If you get into discus you probably would do well to have a "reverse osmosis system". Now saltwater is different. You want distilled water because you want the PH to stay up around 8.0 and up and you want to keep phosphates down, and that is as simple as I can get.