Major pH drops! Help Please!

[gmac]

I have a major problem with my, it keeps dropping badly! My tap water is a pH of about 7.0 so it's perfect, but when I tested it at the end of my cycle a week ago it had dropped to 6.0 and so I bought some pH UP and have been adding a little of it and got it up to about 7.4 and then it drops again in 24 hrs. It did this again last night.

I need it to stay up higher as I have new Mollies as of yesterday. Why would this be dropping?

I have a 30gal tank with 6 plants, 2 black mollies, 1 balloon molly, 6 neon tetras, and 1 siamese fighting fish. Water temp is about 25 deg C.

Could adding Aqua Plus to the water for removing chlorine etc affect things or? I'm totally stumped! Please help!

[Voodoo Chilli]

Stop using the pH Up [acronym:b4f94faae4="As soon as possible"]ASAP[/acronym:b4f94faae4]! These products are usually more harmful than good and will make it difficult to get accurate readings to find out what the problem is.

A few questions:

How long has the tank been set up and is it fully cycled?

Do you perform regular water changes?

What are the [acronym:b4f94faae4="Carbonate Hardness"]KH[/acronym:b4f94faae4] and [acronym:b4f94faae4="General Hardness"]GH[/acronym:b4f94faae4] levels of your water?

What is the pH of your tank water and what is the pH of your tap water after it's been sitting for 24 hours?

[gmac]

The tank has been set up for 3 weeks, and fully completed it's fishless cycle succesfully 1 week ago, we kept it topped up with Ammonia for a week and added fish yesterday for the first time. We have only done one water change so far to bring the nitrate down at the end of the cycle. The gH is about 5, we have soft water and I have not done a kH test. I am going into the [acronym:d0d8e0feed="Local Fish Store"]LFS[/acronym:d0d8e0feed] in an hour, what should I look for?

Thanks.

[Voodoo Chilli]

Do you know what the nitrate levels were? Dissolved organics can cause a pH crash very easily and may be what's causing your trouble.

[gmac]

At the end of the cycle Nitrates were through the roof, 80-160+, but I did a 90% water change two days ago and brought it down to 10ish, so I have a nice level of nitrates right now. I have put in the pH UP twice over the last few days and it doesn't sustain a good level, what should I do instead to get it to rise? I have had green algae and brown algae, we have since reduced lighting hours from 10 to 8 and the green has disappeared, however brown is still prevolent, but the mollies are helping to get rid of it. Could algae cause a pH drop?

Thanks.

[BrianNY]

Most likely the pH drop is caused by your very soft water. To stabilze your pH you need to get your [acronym:bfea25535f="Carbonate Hardness"]KH[/acronym:bfea25535f] over 4. This can be done by simply using a handful of crushed coral in your filter. See if your [acronym:bfea25535f="Local Fish Store"]lfs[/acronym:bfea25535f] will give some.

Side note: Never do more than a 50% water change. Changing more than that is very stressful to your fish.

[gmac]

Originally Posted by BrianNY

Most likely the pH drop is caused by your very soft water. To stabilze your pH you need to get your [acronym:6f70d6eb69="Carbonate Hardness"]KH[/acronym:6f70d6eb69] over 4. This can be done by simply using a handful of crushed coral in your filter. See if your [acronym:6f70d6eb69="Local Fish Store"]lfs[/acronym:6f70d6eb69] will give some.

Side note: Never do more than a 50% water change. Changing more than that is very stressful to your fish.

I did the 90% water change before any fish were in the tank to bring the nitrate levels down - I could afford to lose the free floating bacteria.

My gH was about 5 I think, so that is very soft I assume.

What is crushed coral? And I have not tested my kH yet... right now I am doing 10-20% water changes to sort out the pH issue - my tap water is 7.0 pH so I am hoping the water changes should stabilise things after a while, should that be right?

Thanks.

[mattrox]

Crushed coral is just that....coral which has been crushed, it is calcium carbonate. It will neutralise acidity.

Before you do that......

Take tap water and fill a glass and leave it over night on the bench. Then test the pH...... this will allow any dissolved gasses to equilibrate with the gasses in the air. It could be that your water supply has no dissolved [acronym:8cdd4c8bbc="Carbon dioxide"]CO2[/acronym:8cdd4c8bbc] in it. And then when it is in contact with air the pH drops because of dissolved [acronym:8cdd4c8bbc="Carbon dioxide"]CO2[/acronym:8cdd4c8bbc] and the formation of carbonic acid.

I have a gH of 3 and a kH of 1 and I don't get pH crashes unless the water changes are neglected...... regular 20% changes should work well [acronym:8cdd4c8bbc="Your Mileage May Vary"]ymmv[/acronym:8cdd4c8bbc] with different stocking levels.

[Menagerie]

Take tap water and fill a glass and leave it over night on the bench. Then test the pH...... this will allow any dissolved gasses to equilibrate with the gasses in the air. It could be that your water supply has no dissolved [acronym:54804064e8="Carbon dioxide"]CO2[/acronym:54804064e8] in it. And then when it is in contact with air the pH drops because of dissolved [acronym:54804064e8="Carbon dioxide"]CO2[/acronym:54804064e8] and the formation of carbonic acid.

Yes, that is the proper way to test tap water.
What are the other water parameters (ammonia and nitrite)?