What should the PH be in a fresh water fish tank with guppies and mollies in it?

Question

I have a tank the had 3 male guppies, 4 female guppies, 2 female mollies, and a pelco. Yesterday I lost 1 male guppy and 1 female. They show no outside signs of problems and they were just fine yesterday morning.
I changed 10% of the water last night and gave them a salt bath. Before doing that I tested the tank and my PH was 6.4. All the others were fine. What should the PH be in?
Need to know anything more email me at [e-mail] or just post it on here and I will add to it.

PH -- 6.4
So of you asked what these were so here ya go...

AMMONIA -- 0

NITRITE -- .25

NITRATE -- 0

Answer 1

Thats a pretty low ph, but its better to have a stable ph then one that swings. It is much more likely it was nitrite or ammonia, do you have tests for that?

Answer 2

In theory, it should be near 7.0 for either fish, Mollies like more alkaline water, while guppies slightly acidic. However.....

In you case I would do this:
Check the pH of your tap water ( after it sits in an open container for a few hours) and also call you pet shop and as what the pH in their freshwater tanks are. If your is low, change it slowly by doing small, daily water changes. Try to keep the pH near your tap water pH as those fish will do quite well in a wide range of pH. I do not advocate changing the pH / hardness of a tank unless you have some very sensitive fish that demand a very limited range of water conditions to do well.

Your pH of 6.4 did not directly cause the death of your fish, but may indicate other problems in the tank. You do not mention your water hardness and a lack of carbonate hardness can contribute to a sudden pH drop in the right conditions. It's a long chemical story, but if you want it, just say so and I'll email you. Basically, the less you fool around with the water chemistry or the less you need to, the better.

If the pH of 6.4 is far below tap and the change was sudden, it may be that your ammonia has suddenly and sharply increased. The water changes and a good cleaning of the gravel should help that in a short time.

Best of luck

Answer 3

Meh, I wouldn't worry about it at all. Guppies and mollies are very adaptable fish and do not require a perfect pH to be healthy. Anything from 5 to 8.5 is fine for them. What you need to avoid is rapid pH fluctuations, which can kill fish way more than a slightly off pH ever could. So, test your tap water (leave it out overnight) to compare to the tank water. Also test for carbonate hardness (KH). If your KH is low, pH fluctuations are much more likely to occur, so use baking soda to increase pH.
Add it very slowly (as I say, pH fluctuations kill fish) - add 1/3 teaspoon every hour until the pH is about 7-7.5. Tally how much you used so you know how much you need to put in your new water when you do water changes. However, I do not think this was the cause of death, so I don't think it is necessary to start mucking with the pH.

Mollies are technically brackish fish. I don;t, however, advise giving them a salt bath unless you know why you're doing so. A rapid increase / decrease in salt concentration will mess up their osmotic regulation causing bloating or dehydration. You can add a little aquarium salt (about 1tbsp per 5 gallons) to the tank water at all times, however, to keep the fish healthy.

I suspect that something else killed the fish. What are you ammonia / nitrites? Anything above 0 is toxic. You can also look into other factors like too hot / too cold water (ie heater malfunction), something toxic in the air (spraying an aerosol can, for example, can kill a fishtank), something toxic in the water (is it possible you forgot to use dechlorinator?)

Anyway, I suggest you do a large (50%) water change, add a little baking soda and a little salt. They should be fine :)

Answer 4

The Ph should be anywhere between 5.5 and 8.5. It does not matter as long as it is stable. So do not mess with it.

Not all fish need a Ph of 7. Look up discus and see if they ned a Ph of 7. Look up African Cichlids and see if they need a Ph of 7. I guarantee you will learn that this is not true.