pH dropping

[mmckinniss]

I have a fairly new tank - 55gal freshwater. I've been doing a fish in cycle, which is nearly complete. Nitrites have been present for a couple weeks, with the first hints of nitrates now arriving. I've been doing pwc's every couple days or so to keep ammonia & nitrite levels down. There are six small fish residing here (3 Platies, 3 swordtails). When I began, pH was quite high, around 7.8. Two weeks ago, I was in a more comfortable range, ~6.8. I'm now down around 6.2-6.4. What might be causing this? And how can I raise the pH in a healthy manner?

 

[tamtam]

You can use crushed coral to bring it up naturally. Just get some and put it in a media bag in your filter. It may take some trial and error to get it where you want but start out small and work your way up.

As for why, I'm not really certain. Have you tested your water from the tap for PH and then let is gas off for 24 hours? If not I would suggest you do both. You may have a high PH from your tap but once it gases off it could drop which would explain it. You def want to get it up and a PH that low can stall your cycle. Just put some water out in a container for 24 hours and give it a few stirs through that time and then test it.

 

[vance1013]

You dont want to change your ph to drastically it could result in ph shock what is your tap ph? How regular is your pwc and how much each time? Doing 50% could help with the balancing of ph most fish will acclimate to a level ph

 

[vance1013]

You can use crushed coral to bring it up naturally. Just get some and put it in a media bag in your filter. It may take some trial and error to get it where you want but start out small and work your way up.

As for why, I'm not really certain. Have you tested your water from the tap for PH and then let is gas off for 24 hours? If not I would suggest you do both. You may have a high PH from your tap but once it gases off it could drop which would explain it. You def want to get it up and a PH that low can stall your cycle. Just put some water out in a container for 24 hours and give it a few stirs through that time and then test it.

+1 to that

 

[jlk]

How big/how frequent have your water changes been? What are your numbers for ammonia, nitrite & nitrate? As suggested, test your tap ph straight from the tap then after it has gassed off for 24hrs & let us know what these numbers read.

 

[mmckinniss]

Thanks for the feedback. My water changes have been every 2-3 days at about 20-25%. I'll have to test the tap water. Out of the tap, I know it's on the high side (~7.8). I haven't let it sit 24 hrs. Ammonia has hovered around .25 ppm, nitrites around .25 ppm, nitrates are just now starting to show.

 

[mmckinniss]

Thanks for the feedback. My water changes have been every 2-3 days at about 20-25%. I'll have to test the tap water. Out of the tap, I know it's on the high side (~7.8). I haven't let it sit 24 hrs. Ammonia has hovered around .25 ppm, nitrites around .25 ppm, nitrates are just now starting to show.

OT of the tap, water is pH 8.4. We'll see where it is tomorrow.

 

[jlk]

Thanks! Lets see where your ph sits tomorrow. I would not add any cr coral at this point because your ph straight from tap is quite high. I would just work on increasing your water changes to naturally rebuffer your water & stabilize your ph. Its also possible that your GH/KH may be on the lower side and this may be worth having your lfs check when you have a chance.

 

[mmckinniss]

Thanks! Lets see where your ph sits tomorrow. I would not add any cr coral at this point because your ph straight from tap is quite high. I would just work on increasing your water changes to naturally rebuffer your water & stabilize your ph. Its also possible that your GH/KH may be on the lower side and this may be worth having your lfs check when you have a chance.

What is GH/KH?

 

[jlk]

GH is general hardness (dissolved minerals) and KH is carbonates (buffers). They work together to keep ph stable. These are generally not concerns in a fw tank unless theres an issue with ph crashing that can not be resolved with increasing water changes to naturally restore GH/KH to your water. Your good bacteria use KH to process ammonia. As the KH levels are used up, your ph becomes unstable and will crash. Lets see if increasing your water changes is enough to keep your tank stable while cycling. Heres some more info on the science behind GH/KH:

Water Chemistry: pH, GH and KH What are they all? - Scott Thomson
Aquarium Chemistry; Calcium, KH, GH, pH, Electrolytes, Magnesium, Mineral Ions, Cations

 

[Wyomingite]

What is GH/KH?

GH is general hardness of the water. It is a measure of the amount of disssolved minerals, mainly magnesium and calcium. It can be measured as parts per million (ppm) or degrees hardness (dH). For conversion purposes, 1 dH equals 17.8 ppm.

KH is carbonate hardness, a measure of the bicarbonate and carbonate ions in the water. Both ions have negative charges. This provides the buffering capacity to prevent pH decreases.

pH is a measure of the balance of hydrogen ions and hydroxide ions in the water. Simply put, the more positively charged hydrogen ions in the water, the lower the pH.

GH does not affect pH; KH is the key for pH control. Bicarbonate ions react with excess hydrogen ions to form carbonic acid, which then breaks down into carbon dioxide and water. The carbon dioxide gases off and pH changes little. pH naturally drops in an aquarium as the metabolic processes of livin' critters utilize carbonates and the buffering capacity provided by carbonates decreases.

Very simplified version of what occurs, but adequate for most of our needs as fishkeepers. Hope it helps.

WYite