Low Ph!!

Sorry to read about this.

What percentage of the filter media did you change? If less than a third, for example, it's unlikely that this is the cause - it ought to be quite easy to recoup the good bacteria over the next few weeks unless you're significantly overfeeding.

Presumably you didn't do anything else like run the filter media under tap water (rather than discarded tank water)?

Do you know what your GH and KH / water hardness readings are? If they're very low, then that may account for a PH crash.

Is there anything else which you've added to the tank or done differently?

What is your tap level PH reading normally?

What are the ammonia/nitrite/nitrate readings?

Sorry for all the questions. I'm tempted to suggest a water change, as this ordinarily helps problems, but it might not necessarily be the best course of action, hence all the questions. We'll do our best to help once you get back to us on these questions.

I had the same thing happen to me about 10 years ago, the pH drop I mean. That was when i was very lazy about water changes, doing about 25% once a month. The cause was my low KH getting used up between water changes.

But in your case you had just done a water change - you say you do them weekly, but how much?

Did you remember to add dechlorinator when you did the water change?

Gasping at the surface usually means ammonia and/or nitrite in the water so we will await your test results to see if there is any in the water.


For future reference, the only medium that should be changed is carbon, whether it is impregnated in a sponge or in a cartridge. Though even that doesn't have to be changed - it will stop removing things and work as a home for the bacteria. Sponges and ceramic media should just be washed in old tank water until they literally fall apart.

Yes always use declorinater

No no painting and I don’t use air freshener really especially not near them don’t even light candles in this room I’m reallt confused when it’s been ammonia in the past it was clear what the problem was I’m completely clueless as to what’s happened would you say do a 50% water change now?

Am doing it now I will get rid of 50% of the water I can’t sit and do nothing I feel like if something doesn’t change I’m going to wake up to no fish  fingers crossed

Thanks everyone for the advice! And concern
Just done a big water change and I don’t want to talk to soon but fish and shrimp have all gone back to normal! Shrimp are back on their moss balls and fish swimming mid tank again literally as soon as the new water was in! So confused as to what it was 

No my son is 7 and knows not to do anything silly but the next morning I tested the water to check the ph and found a slight trace of ammonia! I did another big water change and then another today so I’m thinking it did a mini cycle after I changed the carbon, but I’ve been testing my water every few hours and it’s all gone back to normal all my tetras have got their dark red bits back and seen happy I treated them to some frozen worms 

It’s a carbon cartdridge with granules in at the bottom then 2 phosphate sponges theses are the things I only normally need to replace when they are falling apart and a big blue sponge thing on top which lasts for ages, yes it’s all gone back to normal amazing what a few emergency water changes can do!

I agree with Matt.

Wait a couple of weeks, then change 1 phosphate pad for a sponge, any brand will do just cut it to the same size and shape as the pad. Wait a month. Then change the other phosphate pad for another sponge. Then wait another month and swap the carbon cartridge for yet another sponge - or make a slit in the cartridge, empty put the carbon and fill the bag with sponge.

Then all you need to do is wash the sponges in old tank water taken out during a water change when they get covered in brown goo.

Thank you Sue and Matt that sounds a lot less complicated by making it just sponges because they are nice and easy to clean in the tank water when doing a water change I  will do this