Any Idea What Could Be Causing The Ph In My Tank To Lower?

[lordhans]

I have a 100 gallon tank that has been in operation for a few years. I recently started to get into the hobby and am trying to learn about how to provide a good environment for my fish. In checking the tank's water conditions I am getting low pH readings of 6.0 (or possibly lower, the API test kit only reads down to 6.0). I checked my tap water and the pH is in the 7.8-8.0 range-- so its much higher than that of the aquarium. I have done probably 10+ 10-50% water changes in the last 2 months because of a high nitrate level concentration I was having. Because of this I would expect the pH of the tank to be higher, as its being infused with so much high pH tap water. But for some reason the pH seems to lower in the tank very quickly. For example, I did a 20% water change yesterday and the tank's pH went up to 6.6 but when I checked the pH today it is down to the 6.0 (or lower) reading.

My tank is currently understocked and the contents are as follows:
-~Inch think of gravel/rocks on the bottom--typical aquarium stuff that has been in use in various aquariums 10+ years.
-Two pieces of small-medium driftwood that have been in use in various aquariums 10+ years. I also had a large piece of driftwood which is only a few weeks old in the aquarium but I removed it as I read the tannic acid that leeches out can lower pH levels (although I had soaked it for 2 weeks prior like recommended).
-A glazed ceramic 'log' thing.
-A few small granite rocks.
-Several fake plants.
-Two real plants (a Amazon sword and some elodea)
-Two filters (one is a back hanging filter and one is a canister filter with carbon, de*nitrate, and those ceramic things for bacteria to grow on, as its filter media).

Any ideas of what could be causing the lowering pH levels or what I can do to fix this? I was considering using something like API Proper pH but some of the other posts I've read on this forum frown upon using chemicals for things like adjusting pH levels. If I left anything critical out just ask and I will be happy to provide the details.

Edit: I meant de*nitrate, not de*nitrite.

 

[botiaboy]

driftwood and real plants can lower pH and the effects of the other piece of driftwood may still be working... also what is yur hardness? that is a major factor in pH changes. My tap water is around 7 when it comes out but within days it drops to 6 or less,since the hardness is so low, which isnt a problem for me because I have south american and asian fish that like low pH and low hardness like loaches and rams xD depending on what degree of hardness your water is it may fluctuate to a lower pH frequently or refuse to drop from a high pH.

 

[TwoTankAmin]

I don't see any obvious reason your pH should be dropping like that. One possibility is your tap isn't what it appears to be when it first comes out. To insure you are actually testing its ultimate level do the following. Fell a glass with your tap. if you have an air pump and stone, drop in the stone and bubble the water for an hour and then test it. if you don't, let it sit out, uncovered and test it 24 hours later. Also you should test the nitrate level of your tap water using the same kit as you do to test the tank.

The only thing I did not recognize in your info about the tank was something you called "de*nitrite". My hunch is this would not be something ideal for long term use in a fw tank.

 

[lordhans]

driftwood and real plants can lower pH and the effects of the other piece of driftwood may still be working... also what is yur hardness? that is a major factor in pH changes. My tap water is around 7 when it comes out but within days it drops to 6 or less,since the hardness is so low, which isnt a problem for me because I have south american and asian fish that like low pH and low hardness like loaches and rams xD depending on what degree of hardness your water is it may fluctuate to a lower pH frequently or refuse to drop from a high pH.

Driftwood could still be working after almost 10 years of being in a tank?
I'm not sure what my hardness is, the API test kit doesn't have the proper solutions for that..I will have to get a test kit that does. I think that my water is harder than it is soft though--with a good amount of minerals (I get lots of calcium deposits etc.)

I don't see any obvious reason your pH should be dropping like that. One possibility is your tap isn't what it appears to be when it first comes out. To insure you are actually testing its ultimate level do the following. Fell a glass with your tap. if you have an air pump and stone, drop in the stone and bubble the water for an hour and then test it. if you don't, let it sit out, uncovered and test it 24 hours later. Also you should test the nitrate level of your tap water using the same kit as you do to test the tank.

The only thing I did not recognize in your info about the tank was something you called "de*nitrite". My hunch is this would not be something ideal for long term use in a fw tank.

OK, I will set out a cup of water and test it tomorrow to see what sort of measurement I get.
Also, yeah I meant de*nitrate---I think my tank had 'old tank syndrome' and had incredibly high nitrate levels. In addition to 10+ water changes I added one filter bag of de*nitrate to my fluval 305 filter.

 

[The Taffy Apple]

You need one of these ----->
http/cgi.ebay.co.uk/API-Freshwater-GH-KH-Test-Kit-/260550776897?pt=UK_Pet_Supplies_Fish&hash=item3caa095841

I had severe PH problems when cycling both my tanks, PH would drop from a very healthy 7.2 out of the tap to 6.0 overnight, every week. On a couple of occasions it 'stalled' my cycle.

My Kh/Gh test proved i live in an area of very soft water, which was causing my PH 'crashes'.

I added Bicarb Of Soda to my small tank which 'buffered' it up weekly, but with my bigger tank i included some coral gravel into my Fluval 205 and into the tank....the PH has been fine since !

Hope this helps,
Terry.

 

[raptorrex]

driftwood and real plants can lower pH and the effects of the other piece of driftwood may still be working... also what is yur hardness? that is a major factor in pH changes. My tap water is around 7 when it comes out but within days it drops to 6 or less,since the hardness is so low, which isnt a problem for me because I have south american and asian fish that like low pH and low hardness like loaches and rams xD depending on what degree of hardness your water is it may fluctuate to a lower pH frequently or refuse to drop from a high pH.

Driftwood could still be working after almost 10 years of being in a tank?
I'm not sure what my hardness is, the API test kit doesn't have the proper solutions for that..I will have to get a test kit that does. I think that my water is harder than it is soft though--with a good amount of minerals (I get lots of calcium deposits etc.)

I don't see any obvious reason your pH should be dropping like that. One possibility is your tap isn't what it appears to be when it first comes out. To insure you are actually testing its ultimate level do the following. Fell a glass with your tap. if you have an air pump and stone, drop in the stone and bubble the water for an hour and then test it. if you don't, let it sit out, uncovered and test it 24 hours later. Also you should test the nitrate level of your tap water using the same kit as you do to test the tank.

The only thing I did not recognize in your info about the tank was something you called "de*nitrite". My hunch is this would not be something ideal for long term use in a fw tank.

OK, I will set out a cup of water and test it tomorrow to see what sort of measurement I get.
Also, yeah I meant de*nitrate---I think my tank had 'old tank syndrome' and had incredibly high nitrate levels. In addition to 10+ water changes I added one filter bag of de*nitrate to my fluval 305 filter.

you are, of course, right. 10 year old drift wood will have no efect on you water. though i guess it could be rotting and releasing tannins. even so they are good for fish and don't effect PH for too long (even when new).

the only option i can offer iis to use crushed coral as a substrate. this will buffer up the PH, over time. one though, are you adding CO2 for your plants?

 

[TwoTankAmin]

Just to clear up a small misconception in this thread. Its is not general hardness, GH, that keeps pH stable or lets it drop, but rather KH

Buffering capacity refers to water's ability to keep the pH stable as acids or bases are added.

To raise the KH without raising the GH, add sodium bicarbonate (NaHCO[sub]3[/sub]), commonly known as baking soda. 1/2 teaspoon per 100 Liters raises the KH by about 1 dH. Sodium bicarbonate drives the pH towards an equilibrium value of 8.2.

from FINS

 

[lordhans]

As suggested I left out some tap water over night and tested it today (after about 12-14 hours time). The pH tested at about 6.6. This is much lower than the pH measurements I was getting when I tested water directly from the tap.

I will go pick up a GH/KH test and report back.

I am not using C02 for my plants.

If I were to use crushed coral in my filter/substrate how much should I use? (100 gallon tank with 6.0 or lower pH).

Thanks for all the help so far everyone.

 

[botiaboy]

just out of curiousity, what fish are in the tank?

 

[lordhans]

Right now there are 3 bala sharks that are 6-8' (I know there should be 5+ and some consider bala sharks too big for a 100 gallon tank but I sort of inherited the tank from my folks so I'm just going with it for now), 1 blue gourami, and 2 tetra-like fish of some sort.

 

[botiaboy]

well, with those fish I wouldnt worry too too much about your pH. I have the same problem but it's never affected my fish, although I usually choose fish that work well in super soft water. As far as I know bala sharks arent picky and gouramis and tetras actually prefer softer water.

 

[TwoTankAmin]

If you decide to go the crushed coral route be aware that the effects are not instant. basically the process is that the flow through the coral slowly dissolves it and it enters the water. I suggest you start with a bag filed with about one cup of coral and then give it some time (a week or two) to see what the effects are.

The coral is basically releasing calcium carbonate (CaCO3) which is not really soluble in water. However, when other elements are present in the water it will disolve some. Co2 is one thing that promotes the process.

Another thing you can use to raise KH is

sodium bicarbonate (NaHCO[sub]3[/sub]), commonly known as baking soda. 1/2 teaspoon per 100 Liters raises the KH by about 1 dH. Sodium bicarbonate drives the pH towards an equilibrium value of 8.2.

Use this very sparingly as a small amount goes a real long way.

 

[Caprichoso]

The reason your pH is dropping is because of the high nitrates. One could call this "old tank syndrome". This should only be fixed with water changes and very regular tank maintenance like gravel vac. Do not use any chemicals or products to do this as you will create much issues for yourself. You have to perform some larger water changes, like 50%-75% every week plus a very good gravel vac. Also, take the carbon out, it's useless unless you want to remove medication from the water. Add more ceramic rings or sponge to increase your biological filter. You will notice that when you really get your tank cleaned up that the pH will go back to normal. This was my experience anyway.

Good luck!

 

[lordhans]

So it has been a while. I have been doing water changes at least 2-3 times a week for the last month. The water changes varied between 20-40%.

The pH coming out of my tap is ~7.6. I did a test and let the water sit for a few days in a cup and it measured about 6.8 pH.

The last week I have been been using some RO water with a pH 7.0 I got from a LFS. This has accounted for 1/2-1/4 of the water I am using during the changes.

Yet my tank pH still keeps reading 6.0 or less.

Any ideas?

 

[lordhans]

I did a 40% water change and the pH of the tank came up to 6.8.
About 30 hours later I tested the tank and it is back down to ~6.0...

Should I try using some crushed corral? If so, how much should I add at a time? It is a 100gallon tank.