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pH problem in tank

Chez_

Chez_

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4 May 2024
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Somerset
Morning everyone. I have been ineffectually faffing around with CO2 in my 400l tank just using a drop checker for the last couple of weeks. I've had one or two deaths and have gone back to basics. CO2 has been off for five days and I did my weekly 50% water change a couple of days ago.

We have done degassed tests (waiting 24hrs) with an NT Labs Narrow test, that read out at 6.8 for both tank water and tap water. I have just tested straight out of the tank and it's 6.2.

I have an FX6 with a spray bar providing quite a bit of surface agitation.

I feed 40ml TNC Complete three times a week and do a 50% water change once a week.

I knew the pH would be low -- our water comes straight off the sandstone and acidic soils of Exmoor -- and I was thinking a .5 drop in the pH would be all I could aim for. However, that will take it below 6 if I am starting at 6.2.

I think that might be bad for the fish? They're a mixture of nano common community fish, tetras, Corey's, bristlenose, Endler's, honey gourami, chain loaches.

Do I need to abandoned the idea of the CO2? Do I need to think about getting the pH up a bit? I chuck cuttlebone in all my tanks.
 
Usually the comparison of the pH drop is made with the degassed sample, so your 0.5 drop would put you at 6.3. A full 1.0 pH drop would put you at 5.8.

Keep in mind that drop tests have a lot of room for inaccuracies.

It seems to me that most fish manage to adapt to CO2 acidity well enough, but it is hard to understand what is a proper adaptation and what is just painful survival. Nevertheless, I'd expect most of your fishes to be OK. Not sure about the endlers.
 
If you are really worried, you can add some crushed coral to the filter (in a bag) and it should increase (and buffer) the ph. Then, you will feel comfortable that the CO2-induced pH will not be of concern.
I have never done this myself (I live with tap water with a pH of 7.5-8.0) so perhaps some people with experience can chime in.
 
Thanks everyone for your answers. The KH is 2, using the NT Labs hardness test, which doesn't sound like it's too terrible? I have some crushed coral I could add to the filter if necessary, though.
  • Tank size is 400l, but prob 340l filled, I've got lots of wood etc in there. Fluval FX6 with a spray bar that is currently on max, with lots of surface agitation. Two air-stones.
  • CO2: 7am - 3pm, one bubble a second ATM. I've got a JBL Spiral 10 diffuser that is in the corner of the tank under the start of the spray bar and near one of the air-stones. Is that the right place for it? My logic is that it's at the beginning of the current, so CO2 bubbles will travel all the way down the tank.
  • Lights: 50% 9am-11am - 100% 11am-4pm - 50% 4pm-6pm
  • TNC Complete 20ml a day, 200l water change once a week.
I am at home tomorrow and can keep checking on the behaviour of the fish, and then tomorrow night I can test the PH and increase it a bit. Working on the one bubble per second per 80l from George Farmer's book, I should be aiming for four or five. I don't want to do anything quickly though, as I lost a couple of fish whilst faffing around without measuring properly before the holiday.

Any further advice or reassurance would be appreciated. I'm a bit worried it's like a washing machine in there for the fish with the FX6 on max.

1000028166.jpg
 
Chez_ said:
Thanks everyone for your answers. The KH is 2, using the NT Labs hardness test, which doesn't sound like it's too terrible? I have some crushed coral I could add to the filter if necessary, though.
Click to expand...
KH of 2 is perfectly fine. You don't need to change anything here.
Chez_ said:
  • Tank size is 400l, but prob 340l filled, I've got lots of wood etc in there. Fluval FX6 with a spray bar that is currently on max, with lots of surface agitation. Two air-stones.
  • CO2: 7am - 3pm, one bubble a second ATM. I've got a JBL Spiral 10 diffuser that is in the corner of the tank under the start of the spray bar and near one of the air-stones. Is that the right place for it? My logic is that it's at the beginning of the current, so CO2 bubbles will travel all the way down the tank.
Click to expand...
1 bubble per second is wholly inadequate for a 400L tank. If that's a drop checker on the left side of your picture you can see that it is entirely blue indicating that you have added a negligible amount of CO2 under your current conditions. "Bubbles per second" isn't very reliable as a unit of CO2 injection, but I have a tank that is 10x smaller than yours and I inject probably around 3 bubbles per second which gives a not very aggressive CO2 concentration per drop checker... maybe around 10 or 15 ppm.
 
Andy Pierce said:
KH of 2 is perfectly fine. You don't need to change anything here.

1 bubble per second is wholly inadequate for a 400L tank.
Click to expand...

Thanks, Andy. I was going to increase daily and keep testing the PH at the end of the day to see where I am at. If I'm aiming for 30 per second-ish then I will turn it up to say, 10 per second as a starting point today and tweak it up during the course of the week.
 
Chez_ said:
KH is 2
Click to expand...
KH of 4-6 is much easier to manage when injecting CO2. With Hornwort and Vallis - you probably know this, sorry - they are plant species that actually like neutral to hard water and certainly don't need 20-30 ppm of CO2, you could completely rethink your plant choice and exploit your low hardness water and settle for more modest CO2 injection and you could keep a lot of very happy tetras and difficult plants, many of the stem plants love softer water, Rotala Macrandra, Cabomba etc.
Lovely bog wood and sand substrate, and with your soft water, less injected CO2, maybe gentler filtration/surface agitation, a little bit of buffering, lots of soft water plants and soft water fish, and you should see things thrive. Aesthetically I personally don't think your blue background works very well, but more importantly, perhaps, I think a black or brown, or green background settles fish, but that might be an anthropomorphism!
I wish you well, I play with my water hardness but sometimes think I should work with the liquid concrete from the tap - my choices for a hard water would be Vallis, Hornwort and some of the crypts available.
 
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