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Joan, Vet Technician
Category: Pet
Satisfied Customers: 18676
Experience:  Vet Tech for 35+yrs. Small Animals and Fish
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This is an aquarium water pH question. We have a 30 gal

Customer Question

This is an aquarium water pH question. We have a 30 gal fresh water tank that has been going with guppies for 6 years. In December our filter died, along with all of our fish. We cycled the tank and replaced the filter with a dual carbon filter. Now we cannot keep the aquarium water pH low enough for fish to survive. Our house water is very basic, off the chart when we test it. We add aquarium acid to the water and can get the pH to 6.8, but three days later the aquarium water pH is back up to around 8.0+. We have 6 different products recommended by two pet stores, but none keep it lower than 8.0. We cycled the tank twice since December, and currently we have only one fish and one snail. We've added fish very slowly, 3-5 at a time, but they die within 3 weeks. I am wondering if the filter is raising the pH to unacceptable levels. This appears to be a new problem, since our guppies lived for years without issue. I do not know if our water pH changed, or if the filter is raising it in the tank. Any ideas?
Submitted: 1 year ago.
Category: Pet
Customer: replied 1 year ago.
I'm sorry, we added a black light in March. Will a black light affect pH stability? Our new filter is the Penguin Bio Wheel 350 by Mainland. It's for a 50+ gallon tank, ours is 30 gallons (we were in a crisis and it was the only filter they had in stock. Bigger is better, right?.) The pet store recommended a blue light, but it looks like we purchased a black light by mistake. We just discontinued its use today.
Customer: replied 1 year ago.
The filter is by Marineland. It gets autocorrected.
Expert:  Joan replied 1 year ago.


My name is ***** ***** I have been a Vet Tech for 30+ years and a fish keeper for over 40+ years.

There are several natural ways to reduce ph. The one way I love is using a Piece of Driftwood in the tank. It looks nice as well as well as will lower the Ph and keep it balanced. Another way is to set up a second filter with a Peat Moss bag, instead of a charcoal filter. This too works well naturally to lower and balance the PH in a fish tank. You can read more about the natural ways here:

The chemicals when used to lower the PH can throw off the whole tank so in my opinion, it is better to do it naturally.