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I'm having trouble keeping pH at 7.0 in one of my planted tanks, it started dropping a few days ago and are at around 6.4 now. Dosing it with chemicals makes the tank very unstable, anyone know how to raise the pH and keep it stable at 7.0-ish?
 

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Sorry I don't know the answer. I would imagine it would be a easier to raise ph than lower it, crushed shells etc? Since soft water means lack of minerals. Easier to add than subtract mineral I would imagine. I given up lowering my ph for my tank as my locale have fairly hard water probably a 9 ph.. I use to use white vinegar but that is really short term and it last a day or less before it is hard again. Now I focus on plants that grow well in hard water like hornworts, anacharis, vals.
 

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Before you try messing around with pH what are the other parameters, especially KH and Nitrate? Good idea to test the tank and tap water with all the tests you have, and then to repeat the pH test on the tap water that has sat out for 24-48 hours.

Carbonates are one of the most common buffers in aquariums. If the KH is dropping for some reason, the pH is highly likely to drop. KH can drop for any of several reasons, for example, water changes with water that is low in KH, and certain plants will utilize KH as a source of carbon, there are other things going on in aquariums as well that can lower the KH. Certain substrates remove the KH from the water, allowing the pH to drop.

The link between nitrate and pH is this: In a tank with few water changes and rising nitrates the KH and pH will get lower. It is part of a group of things that happen. Look up Old Tank Syndrome and see if this is going on.

If I told you that baking soda is the cure for the problem without helping you to see what else might be going on this would not be a proper answer.

IF you discover that the KH is dropping for some reason, and can figure out why you may decide that adding a source of carbonates can help. Crushed coral, oystershell grit sold for caged birds, limestone based sand or fine gravel are all possible sources of carbonates, as well as calcium and magnesium. (Have you checked the GH, too?) Baking soda is a source of carbonates without the other minerals, but does add sodium to the tank.

IF you discover that your tank is suffering from Old Tank Syndrome, suggested by rising nitrates, then adding baking soda will not solve the underlying problem. You need to remove nitrogen from the tank faster, and other organic wastes either by improving conditions so the plants can help you out, or by increasing the water changes (or both).

IF you find out that your tap water's pH drops after being exposed to the air overnight you may have to figure out some other solution, starting with talking with the water company about their water chemistry.
 

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I'm having trouble keeping pH at 7.0 in one of my planted tanks, it started dropping a few days ago and are at around 6.4 now. Dosing it with chemicals makes the tank very unstable, anyone know how to raise the pH and keep it stable at 7.0-ish?
pH 6.4 isn't that bad. However, if it keep dropping below this, you may have more fish and nitrification than the tank can handle. Nitrification often causes tanks to go acid.

A little sodium bicarbonate wouldn't hurt, but its only a short-term fix.

If the pH continuously drops, the tank is out of balance. I've never had any luck managing pH with chemicals.

I would promote plant growth. Their photosynthesis will bring the pH up and naturally recharge the "alkalinity battery". A soil substrate also helps. Anaerobic processes in the soil consume acidity.
 

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This Hobby is broad and deep; could keep ten people busy for very long lifetimes and they would not know it all. ph is not an easy concept and we are learning all the time. It is not settled just what effect ph has on fish and exactly how it is related to other parameters.

Gererally mains water or the treated water coming out of your tap, unless you have well water, is buffered up to a ph higher than 7.0 (sometimes 8.3 or more) so that the water does not eat your pipes. Buffering is the ability to resist ph change. In water that is buffered a lot, the ph will not shift until the buffer is exausted, then the change can be dramatic and seemingly very fast.

Chlorine (important sidetrack here) is also another of the additives (it affects ph) that is widely misunderstood. Chlorine is not stable in water meaning it wants to come out of the water. Chlorine does not kill everything, it merely suppresses some "bugs" and they multiply quickly once the Chlorine dissipates. Chlorine "removers" do not remove Chlorine they usually neutralize it until it is gotten rid of. Aeration, heating and agitation are all some of the things that get rid of Chlorine.

You are being given very good advice. Do not mess with the ph just because it does not look perfect, ph does not(by itslf) seem to affect fish under normal circumstances and once you start fooling with it the struggle is constant and for most folk not a winning proposition.
 
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