The short answer is, it's best for your fish to not control water quality by adding stuff to the water.
There's this issue called osmotic stress, that you can't really measure, and it has to do with the amount of stuff in the water. Just as people don't do well with too much stuff in the air, fish don't do well with too much in the water or fast changes in how much stuff is in the water.
Like they said, ammonia gets reduced by having a colony of good bacteria to eat it. That makes nitrite, which another bacteria converts to nitrate.
So you want bacteria keeping ammonia and nitrite at zero, and you use water changes to keep the nitrate below 20. Water changes also keep PH stable.
The only time to add stuff is if your tapwater is extremely soft. Some minerals are necessary for the fish, and to balance pH. But if pH starts to move, it's because the pH buffering minerals all have stuff stuck to them so you take some out and out fresh in with a water change.
Hope the chemists in the room will forgive my rough explanation ...
PH can be like 6.5-7.5 according to our LFS, as long as it's stable. For fish stability is more critical than exact numbers.
You can grow your bacteria either by putting in a few fish and doing lots of water changes and water testing to keep the toxins down (fishin cycle) or by adding janitorial ammonia to an empty tank and testing often until ammonia and nitrite are zero, then you do a big water change and then add fish (fishless cycle). The bacteria need ammonia to grow, using bottled ammonia over a live source is often preferred. Dr Tims sells the right ammonia and some bottled bacteria, lots of fishless cycles go faster with baking soda and a high temp and high aeration.
This really is much less a pet than a hobby. Good luck!
Lots of good info here.
Some fish (Neon Tetras, for example) don't respond well to sudden pH changes. Many other species can handle abrupt pH changes *if* it's only due to a change in concentration of carbon dioxide dissolved in the water (plants consume more CO2 during photosynthesis during the day, not so much at night, so pH levels fluctuate over the course of 24 hours). BUT, if your pH change is due to a change in ion concentration in your tank (say, you've adjusted your tank pH to 8.2 with carbonate or bicarbonate, and then you do a 50% water change with soft, pH 7.4 tap water), that's bad news because of the sudden change is osmotic pressure. For the same reason, doing a 50% water change to remove high levels of nitrates can also be problematic. Keep your weekly water changes down to the 20-25% range. If this isn't possible for some reason or your tank water conditions are far-removed from your tap water chemistry, you'll need to pre-treat your fresh water to match the hardness of your tank water. It's often much easier to stock your tank with species that are roughly compatible with your tap water. (I have very soft tap water that's about pH 7.4, so I can keep South American tetras and rams without too much extra work.)
If you do a fishless cycle (with or without bottled bacteria or established filter media supplements), make sure you do the following...
1. Adjust your tank temperature to the low 80s.
2. Maximize the aeration of your tank (bubble wands are good, and even lowering the level of your tank water so that your filter output splashes harder when it hits the surface of the water helps).
3. Make sure that your pH is in the 7.5-8.0 range. If your pH goes below 6.5 or higher than 8.5 or so, your bacteria won't work as well and may even die.
4. Make sure that your tank's KH (carbonate level, or buffering capacity) is 100 ppm or so. The nitrifying bacteria that you grow during the cycle produce acids that slowly lower the tank pH. You need enough buffering capacity to counteract this.
5. Don't let your tank's ammonia or nitrite levels exceed 5 ppm at any time. This will "poison" your nitrifying bacteria and slow your cycle.
6. Don't use Prime or any other ammonia-binding water treatments during your cycle. This will slow your cycle. Seachem claims that the ammonia bound by Prime can be used by nitrifying bacteria, but not everybody agrees with this. If you need to do a partial water change for some reason, treat your fresh water 48 hours ahead of time (Prime only binds ammonia for 48 hours).
thanks!
