Cycling & PH Help

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Robbo80

Aquarium Advice Newbie
Joined
Apr 2, 2025
Messages
2
Location
Uk
Hi guys, just after a bit of advice. I've just set up my aquarium and started the cycling process. I'm currently on day 5. I'm a bit worried about low PH and my cycle stalling. I live in a soft water area.

My results so far are

DAY 1 (Before Ammonia)
PH=7.8
AMMONIA=0
NITRITE=0
NITRATE=0
AMMONIA ADDED

DAY 2
PH=7.8
AMMONIA=2.0ppm
NITRITE=0
NITRATE=5.0ppm

DAY 3
PH=7.2
AMMONIA=1.0ppm
NITRITE=0.25ppm
NITRATE=5.0ppm

Ammonia added after test

DAY 4
PH=7
AMMONIA=2.0
NITRITE=0.50
NITRATE=5.0

Day 5 Results
PH 7
Ammonia=2.0ppm
Nitrite=1.0ppm
Nitrate=10ppm

Just for reference I am using Dr Tims Ammonia and FritzZyme TurboStart 700 and my tank is 240 litres (I think about 55 gallons US)

It was a bit tricky to read today's (day 5) results. PH is still either at 7 or just coming to 6.8, it was really hard to tell.

Interesting to me is the Ammonia was difficult to read, at the very least it's not changed from yesterday at 2.0ppm but it could have even rose a little to 4.0ppm. It was very hard to tell matching the chart colour. I expected the Ammonia to drop as before. It went down from 2.0ppm to 1.0ppm the day after adding Ammonia last time.

I purchased a API GH & KH test kit and my tap water i think is reading at 0 KH (test went straight to yellow with no blue) and GH is 5 = 89.5.

Looking at my results do you think my cycle will stall? I'm seriously thinking of getting some crushed coral, but then I hear other people say to use something like baking soda. I don't like the idea of constantly having to add chemicals. There is a vast wealth of information but some of it is contradictory.

Should I do a 30% water change to try and keep PH up tomorrow?

Any help or advice is most welcomed. I'm a relative novice to fish and aquariums, I'm trying to research and gain knowledge but need a bit of a nudge.

Many thanks
 
Last edited:
If your KH is zero, then your aquarium won't cycle. The process that turns ammonia to nitrite to nitrate uses up KH and once it's gone the nitrogen cycle stops functioning. There is some conversation that maybe in low pH, KH environments that the nitrogen cycle gets its carbon from other sources like disolved CO2, but if this is the case it's much slower to establish.

Your profile says you are UK based, so its not likely your KH is zero, but it could be low, particularly if you are north west, south west Scotland or Wales. You should be able to get your tap water parameters from your water company, which will be more accurate than any test.

It's a bit weird that your KH is low, but pH is high. Low KH usually causes low pH, so that's something worth double checking with your water company.

Low KH will get used up pretty quickly, so your cycle may start, then stop again until KH is replenished with a water change, then start to establish again. But never really get going. It takes about 7ppm of KH to cycle out 1ppm of ammonia, so if you have say 1 degree of KH (18ppm), that would get used up by cycling out about 2.5ppm of ammonia. While doing a fishless cycle you are dosing far more ammonia than a tank full of fish will produce, so the KH gets depleted much quicker while cycling than it does during normal operation. It may be that once you are actually cycled you can keep the KH positive just by regular water changes, but that really depends on how low your KH is and how heavily stocked your aquarium is.

IMO you have a couple of options.

You can forget about cycling altogether. Let the KH deplete, which will lower your pH. The nitrogen cycle will stop functioning, but at pH below 7 your ammonia is non toxic ammonium. Just let the ammonia build up between water changes, and keep fish that do well in acidic, soft water.

Or, address the low KH which will also stabilises the pH. Crushed coral will slowly disolve, raise your KH to some degree, stabilise your pH and keep your cycle functioning. Crushed coral will also raise general hardness (GH). Mixing baking soda in the water will similarly raise KH and stabilise pH, without affecting GH. Baking soda will add sodium into the water too, which isnt always a good idea if you want to keep fish that suit low disolved solids. Alkalinity Buffers will also raise KH without affecting GH.
 
If your KH is zero, then your aquarium won't cycle. The process that turns ammonia to nitrite to nitrate uses up KH and once it's gone the nitrogen cycle stops functioning. There is some conversation that maybe in low pH, KH environments that the nitrogen cycle gets its carbon from other sources like disolved CO2, but if this is the case it's much slower to establish.

Your profile says you are UK based, so its not likely your KH is zero, but it could be low, particularly if you are north west, south west Scotland or Wales. You should be able to get your tap water parameters from your water company, which will be more accurate than any test.

It's a bit weird that your KH is low, but pH is high. Low KH usually causes low pH, so that's something worth double checking with your water company.

Low KH will get used up pretty quickly, so your cycle may start, then stop again until KH is replenished with a water change, then start to establish again. But never really get going. It takes about 7ppm of KH to cycle out 1ppm of ammonia, so if you have say 1 degree of KH (18ppm), that would get used up by cycling out about 2.5ppm of ammonia. While doing a fishless cycle you are dosing far more ammonia than a tank full of fish will produce, so the KH gets depleted much quicker while cycling than it does during normal operation. It may be that once you are actually cycled you can keep the KH positive just by regular water changes, but that really depends on how low your KH is and how heavily stocked your aquarium is.

IMO you have a couple of options.

You can forget about cycling altogether. Let the KH deplete, which will lower your pH. The nitrogen cycle will stop functioning, but at pH below 7 your ammonia is non toxic ammonium. Just let the ammonia build up between water changes, and keep fish that do well in acidic, soft water.

Or, address the low KH which will also stabilises the pH. Crushed coral will slowly disolve, raise your KH to some degree, stabilise your pH and keep your cycle functioning. Crushed coral will also raise general hardness (GH). Mixing baking soda in the water will similarly raise KH and stabilise pH, without affecting GH. Baking soda will add sodium into the water too, which isnt always a good idea if you want to keep fish that suit low disolved solids. Alkalinity Buffers will also raise KH without affecting GH.


That's some excellent info thank you. I am from the UK in Birmingham but I believe the water is from Wales. I will give it some thought but leaning towards trying to carry on fishless cycling.

I might research to see if there are any fish that would thrive in my current parameters. Would be much easier i guess. I've got my heart set on some Pearl Gourami's so if they do okay it's a matter of finding other suitable community fish.
 
Severn Trent same as us? Yes their water into Birmingham is supplied from Wales, so it will be very soft and the pH is on the higher side. Must have some unusual mineral content to have low KH/ high pH. I'm not sure how that works.

A general figure from Severn Trent for KH in the Birmingham area is about 40ppm or just over 2 degrees. You can narrow that down to your postcode online yourself if you wish. Get the Hardness Clark figure and multiply by 14 to get KH roughly in ppm. Roughly 18ppm to 1 degree of KH, whichever is your preferred unit.

Regardless of actual number, that KH is low and will deplete quite quickly. If you are wanting to cycle the aquarium rather than just let everything get acidic, I would get that up higher. With the high pH, I'm not sure that crushed coral will actually disolve to any meaningful degree, you would have to give it a go and see what happens. You might find that as the KH depletes, and the pH drops, that the crushed coral balances everything out and keeps things stable. Would be interesting to know how things go.
 
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