Can diatoms cause pH to rise?

[Fishy monkey]

I've a 43gallon tank, set up for 3 months, in a slow fish in cycle with 5 pearl danios and 5 congo tetras (lost 1 tetra last week but all params were normal).

I have gravel, plastic plants, ornamental cave and driftwood in it, the last new piece of decor was about a month ago. Also has an airstone.

Started with diatoms about 2 weeks ago. My pH has always been a steady 7.6, but when I tested yesterday it was 8.0 and today after a water change it was 8.2. I can't think if anything other than the diatoms that would cause it to rise, but I can't find anything online to suggest it could be related.

Other parameters- ammonia- 0-0.25, nitrites- 0, nitrates- 0-5.

My other tank, a 60 litre that's nearing the end of its fishless cycle has a pH of 6.4 after a water change. It was 6.0 yesterday.

Any advice on what I can do to stop my pH rising and what may have caused it will be gratefully received. I'm terrified its gonna kill my fish if I don't stop it but all advice seems to be not to use artificial means (like pH down).

 

[BBradbury]

Algae & pH

I've a 43gallon tank, set up for 3 months, in a slow fish in cycle with 5 pearl danios and 5 congo tetras (lost 1 tetra last week but all params were normal).

I have gravel, plastic plants, ornamental cave and driftwood in it, the last new piece of decor was about a month ago. Also has an airstone.

Started with diatoms about 2 weeks ago. My pH has always been a steady 7.6, but when I tested yesterday it was 8.0 and today after a water change it was 8.2. I can't think if anything other than the diatoms that would cause it to rise, but I can't find anything online to suggest it could be related.

Other parameters- ammonia- 0-0.25, nitrites- 0, nitrates- 0-5.

My other tank, a 60 litre that's nearing the end of its fishless cycle has a pH of 6.4 after a water change. It was 6.0 yesterday.

Any advice on what I can do to stop my pH rising and what may have caused it will be gratefully received. I'm terrified its gonna kill my fish if I don't stop it but all advice seems to be not to use artificial means (like pH down).

Hello Fishy...

Don't recall the term for this, but if you have a sudden growth of algae in the tank (algae bloom), a lot of carbon dioxide is used up by the plant and it releases oxygen. Water high in oxygen is more acidic, a higher pH.

Large, frequent water changes is the best means of keeping the water chemistry steady. I remove and replace half the tank water every week and algae seems to stay under control and the pH is pretty constant.

B

 

[Fishy monkey]

Hello Fishy...

Don't recall the term for this, but if you have a sudden growth of algae in the tank (algae bloom), a lot of carbon dioxide is used up by the plant and it releases oxygen. Water high in oxygen is more acidic, a higher pH.

Large, frequent water changes is the best means of keeping the water chemistry steady. I remove and replace half the tank water every week and algae seems to stay under control and the pH is pretty constant.

B

Thanks for the info, by plant using up carbon dioxide do you mean the algae? I do 2, sometimes 3 water changes a week of at least 25% cos of it being in cycle. Would a co2 thingy (I've seen something in the lfs that releases co2 but I've never had live plants so i don't know what they're called) or a bottom feeder help? I was going to get either a bn pleco or a SA bumblebee catfish this weekend, but with my pH fluctuating I held off.

 

[BBradbury]

Algae & pH

Thanks for the info, by plant using up carbon dioxide do you mean the algae? I do 2, sometimes 3 water changes a week of at least 25% cos of it being in cycle. Would a co2 thingy (I've seen something in the lfs that releases co2 but I've never had live plants so i don't know what they're called) or a bottom feeder help? I was going to get either a bn pleco or a SA bumblebee catfish this weekend, but with my pH fluctuating I held off.

Hello again Fishy...

Yes, algae is a plant, just like the rest of them in the tank. The difference is, the algae is a primitive, one celled plant. The other aquarium plants are more complex, many celled.

Multiple, small water changes are fine during the cycling process. Afterward, I suggest removing half the tank's volume once a week. If you're going to all the work getting out the gear for a water change, just get it out once and spend a bit more time removing half the water. It's a better use of your time and the fish will be healthier.

Plecos are good algae eaters, so are "Ramshorn" snails. Don't know anything about CO2 systems. My tanks are low tech.

B

 

[jlk]

I would suggest testing your tap water straight from the tap then after it has gassed off for 24hrs. Simple things such as a lack of rain/snow or an excess of rain/snow can cause variations in your taps ph (as well as other parameters). Changes in how the water is processed can effect ph as well. If something seems 'off' in a cycled tank, always start with the water your putting in it first before ruling out other possibilities.

I honestly dont believe the diatoms are having any effect on your ph and from what I have read, theres actually studies that have shown they have mechanisms for natural ph buffering capabilities in nature.

I also would do a big water change on your other fishless tank to raise the ph/buffer levels. A ph of 6 (or lower) will crash your cycle.

 

[Fishy monkey]

I would suggest testing your tap water straight from the tap then after it has gassed off for 24hrs. Simple things such as a lack of rain/snow or an excess of rain/snow can cause variations in your taps ph (as well as other parameters). Changes in how the water is processed can effect ph as well. If something seems 'off' in a cycled tank, always start with the water your putting in it first before ruling out other possibilities.

I honestly dont believe the diatoms are having any effect on your ph and from what I have read, theres actually studies that have shown they have mechanisms for natural ph buffering capabilities in nature.

I also would do a big water change on your other fishless tank to raise the ph/buffer levels. A ph of 6 (or lower) will crash your cycle.

Thank you, we have had a lot of rain recently, I've put a glass of water out and will test it tomorrow. If it is the tap water is there anything I can do about it? I know that an unstable pH can have adverse effects on fish health so I don't want to bring it down too quickly but I don't want it to keep rising either.

My other tank- I did a 50% change yesterday, I'll test the pH again later when it's daylight and if its dropped I'll change some more. Ammonia is still dropping so its not stalled yet