pH issue?

[xawen]

Hi all,

I have a 55 gallon tank, lightly planted about half stocked that's been running for about 4 months. It's got regular aquarium gravel and a Fluval 305 filter with just bio media and sponges.

I did an Ammo, Nitrite, Nitrate test last night and decided to do a pH test too. I don't test pH very often because it's typically been stable and I don't really know what I could do to adjust it if I don't like the numbers.

My tap water runs at a pretty high pH, around 8.2-8.4. The tank's pH tested in the mid 6's. I borrowed a friend's hardness test and found out that my carbonate hardness is basically 0. I knew my water was pretty soft (town water supply), but no idea it was that low.

So I have two questions...

Short term, I'm going to need to do a water change in the next few days. With such a large difference in the tank and tap pH, how can I do that safely? I don't have enough space/buckets to age that much water for 24 hours...if that would even help. I did a water change about 4 days ago (and have been doing them about once a week) without any signs of stress from the fish.

Second, what can/should I do to keep the tank pH closer to the tap pH?

Thanks!

 

[Terrance]

keep a small piece of limestone inside your tank to increase your gh/kh. or you could add crushed coral to your filter.

 

[librarygirl]

Have you kept a glass of tap water out for a day or two to test it and see if the PH changes? My tap water PH is 8.4 but after it gasses out it goes down to about 7.4-7.6. So for water changes I allow the water to gass out in a rubber tub with an air stone (I'm not sure if this is totally necessary but I like to err on the side of caution when it comes to my fish lol). How often do you do water changes? As Terrance said, if your PH is dropping that significantly after 4 days then you may want to try to naturally buffer it by adding a pinch or two of crushed coral or crushed argonite in your filter (I do this as well).

 

[gabysapha]

Have you kept a glass of tap water out for a day or two to test it and see if the PH changes? My tap water PH is 8.4 but after it gasses out it goes down to about 7.4-7.6. So for water changes I allow the water to gass out in a rubber tub with an air stone (I'm not sure if this is totally necessary but I like to err on the side of caution when it comes to my fish lol). How often do you do water changes? As Terrance said, if your PH is dropping that significantly after 4 days then you may want to try to naturally buffer it by adding a pinch or two of crushed coral or crushed argonite in your filter (I do this as well).

That's so interesting because mine comes out of the tap at 7.6 but rises to 8.6 after a day or two.

 

[OasisKeeper]

That's so interesting because mine comes out of the tap at 7.6 but rises to 8.6 after a day or two.

I'm gonna scratch my head on that one for a bit I think. Either that or our resident chemist will roll in.

 

[gabysapha]

I'm gonna scratch my head on that one for a bit I think. Either that or our resident chemist will roll in.

Another aquarist on this forum thinks my city water treaters add something to the water to keep it low out of the tap, but once it gasses out the true ph of 8.6 shows up? Who knows!

 

[adeebm]

Sometimes tap water contains elevated levels of CO2, which depresses the pH. When the CO2 levels reach equilibrium with the air, your pH will rise. The opposite could hold true, if there was a higher level of CO2 in the atmosphere. In the OP's case, if the KH is low or close to 0, then acid released from biological processes in the tank is causing the pH to drop. You'll want to raise the KH, with something like crushed coral or a commercial additive.

--Adeeb

 

[xawen]

Thanks for the advice guys.

keep a small piece of limestone inside your tank to increase your gh/kh. or you could add crushed coral to your filter.

I ran out today and got some crushed coral and filter bags. I have about half of the top tray of the canister filled with the coral right now. Is too too much (flow is still fine), or can I leave it like that until the coral gets eroded?

Once the kh comes up a bit, I assume the pH will stay around where it is now? Should I just plan on a series of small PWCs to bring it closer to the tap pH?

Have you kept a glass of tap water out for a day or two to test it and see if the PH changes? My tap water PH is 8.4 but after it gasses out it goes down to about 7.4-7.6. So for water changes I allow the water to gass out in a rubber tub with an air stone (I'm not sure if this is totally necessary but I like to err on the side of caution when it comes to my fish lol). How often do you do water changes? As Terrance said, if your PH is dropping that significantly after 4 days then you may want to try to naturally buffer it by adding a pinch or two of crushed coral or crushed argonite in your filter (I do this as well).

With a kh that low, I'm sure the tap water pH will drop after some time...I just don't have anywhere safe to store 10-15 gallons of water for a day (cats will be swimming in it).

I've been doing 20-30% PWCs once every 7 or 8 days. I've never noticed any stressed behavior from the fish (BN pleco, Otos, BS Tetras, Gourami and Corys) even though the tank pH must be going up when I do the changes.

 

[xawen]

Another question about the coral in the filter. How quickly does this typically start to affect water parameters (55 gal)?

I want to keep an eye on it as it adjusts, but the hardness test kit is borrowed so I don't want to burn through all the chemicals

 

[librarygirl]

I think it's fairly fast. You may only need a little, it depends on your tank though since yours is large. I only use a pinch in my 20 gal. Just keep an eye on the PH over the next week or so and see if it stays stable. If it starts rising too high you may want to take some out.

 

[xawen]

I think it's fairly fast. You may only need a little, it depends on your tank though since yours is large. I only use a pinch in my 20 gal. Just keep an eye on the PH over the next week or so and see if it stays stable. If it starts rising too high you may want to take some out.

It's definitely moving. In about 30 hours, the pH has risen from 6.6 to 7.6. A bit faster than I would have liked, but the fish look ok. Appetites are good and they're all active. The kh has come up to somewhere between 1 and 2...but it's at least measurable now.

I have about 1 - 1.5 cups of coral in the filter. I've seen people talking about tweaking the amount to get the pH just right. My main goal is to get the pH stable. I hear it erodes, and I'd rather always keep enough in the filter to keep the kh up and pH stable than constantly worry about how much is in there to hit a target pH.

There must be a limit to how high it can go, even if I had an entire canister full of it filtering 1 gallon of water. So...how high will the coral naturally take the pH? If it's in the range if my tap water, is there a reason I can't leave a large amount in the filter all the time?

 

[xawen]

Figured I'd post my experience so far just in case anyone finds this thread later. I added about 1 - 1.5 cups of crushed coral to my canister filter on a 55 gallon tank 4 days ago.

The crushed coral has increased my kh just like I needed. It's doing it fairly slowly, and is up to about 2 degrees. The pH has also been very stable since the kh started to rise.

The coral did abruptly raise the pH in the tank. It rose from around 6.4 to 7.6 in less than a day. Fortunately my fish dealt with the change ok, but it would have been better to add it in stages to control that rise. 7.6 seems to be the limit of what it will take the water up to, and I'm very happy with that number.

I also discovered the very high pH in my tap water drops in a matter of minutes. If measured straight out of the tap, it's around 8.6. If I fill my water change bucket and take the sample from there, it's around 7.8. Since my tank is stable at 7.6, I'm very happy with 7.8 for water changes.

Short version: if you have low/no kh, I highly recommend going the crushed coral route to prevent pH crashes. If your tank pH has already fallen, just watch the pH closely as you add the coral to your filter. It will probably rise in a matter of hours.