PH swing at water change causing deaths?

[Masha]

I've been having some problems with mystery deaths of otherwise healthy looking fish. I lost three peppered cories and two bronze cories, as well as a honey gourami over the last three months.

I suspect that the problem is that the PH in the tank drops steadily through the week, so that when I do a water change, there is an abrupt PH swing which harms the fish.

I tested the tankwater just before doing a waterchange, and PH is about 7.5
Tapwater is 8 after outgassing cholrine.

I think what's happening is that there is a lot of waste in my tank which is being processed by the BB, but as a result there is a drop in PH. I seem to remember BB processing can cause a drop in PH if there is too much waste to process?

I don't think it's the driftwood causing that PH drop, as it's no longer leaching tannins.

So my questions are:
1) Could this be the cause of mystery deaths - doing a 50% water change with water of a different PH?

If so, what's my best solution?
1)Do a very thorough gravel and tank clean?
2)Do a smaller percentage water change?
3)Do more water changes - e.g. two a week?

The tank details are:

Cycled, 23 gallon tank, Tests 0% ammonia, 0% nitrites, and somewhere between 0-12 on the nitrate test a week after a water change. I use an Aquaclear 70 filter.

Tank has many live plants, tough ones like java fern and anubias, as well as a external philodendrum that dangles its roots in the water. Also some driftwood which has stopped leaching tannins as far as I can see.

I do a 50% water change every week.

At the moment, my tank has 8 black widow tetras, 3 silver-tip tetras, 1 bronze cory, 1 java loach, 1 apple snail. They all seem well and happy.

I've been feeding them very minimally (in another thread, people have suggested that I must up the feeding as that might be the cause of the deaths)

 

[Fresh2o]

Long time no talk . If the pH is fluctuating, then I suspect that there is a lack of buffers to stabilize the pH. Have you checked the KH and GH? I am no expert on the numbers so hopefully someone else will chime in on this. The addition of crushed coral will gradually increase the hardness of the water.

 

[Masha]

Long time no talk . If the pH is fluctuating, then I suspect that there is a lack of buffers to stabilize the pH. Have you checked the KH and GH? I am no expert on the numbers so hopefully someone else will chime in on this. The addition of crushed coral will gradually increase the hardness of the water.

I haven't checked KG and GH. I was hoping to avoid having to buy yet more test kits! I can't get the API testkit over here, so have to buy each test separately. But if I have to, I have to, I guess.

 

[Fresh2o]

In that case you could add a small amount of crushed coral and measure the pH over the course of the week and see if it still drops. If yes, then add more and repeat testing.
You could try contacting the water authority and see if you can get an analysis report of the tap water.

 

[Caliban07]

I masha

You are right, the conversion of waste products in the tank by BB does lower ph. The process creates acids and uses alkalinity (kh) having said that, if your tap water is high in buffers then you shouldn't really have a problem.

Like you say, the driftwood will be naturally lowering the ph and ph will drop further at night if you have a lot of plants as plants give off co2 at night rather than take it in. Since co2 in water is in the form of carbonic acid, the ph will drop.

Again this is all a moo point if your tap water is well buffered. If you are unsure you can add crushed coral like fresh 02 said but usually, changing the water weekly is enough.

Water companies can also alter the chemistry of the tap water at any given time so you should check tap water regularly. My tank ph settles at 7.6 and my tap water is around 8.

I'm not changing out all of it. Just 30% a week. I wouldn't expect the tank water to shift that dramatically enough to provoke fish deaths. It certainly doesn't in my tank.

One pattern my tank had similar to yours is in the fact that I too had Cory's and honey gouramis and they all died. I put it down to not feeding enough.

Fish get used to patterns and routines. Even if the ph does fluctuate slightly the fish become acclimatised to what the water is doing. They have too. It's when there is a massive shift in water chemistry in an established tank that can harm even the healthiest fish.

Have you altered anything of significance lately or changed your routine?


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[icydeath]

Another thing you can do (fresh2o and i tend to have differing, yet equally correct and right solutions. we just seem to think differently. at least we get to the same result! ) is that you can do more frequent water changes. 3 times a week at smaller intervals? For example if you normally change 30% of your water, start changing 10% instead. You should also look into your natural buffers like fresh2o said.

The equation to what I said (sorry im a big numbers guy) is 7.5(0.9)+8(0.1) = x
Let x = your end result pH
6.75+0.8 = x
7.55 = x

That way, your pH is only fluctuating by 5 hundredths of a degree.

By the next water change, the pH will probably go back down and you are good.

This works even better if you only change 20% normally and change it twice a week.

Best of luck, Raymond

 

[icydeath]

You could probably stand to do a smaller water change... But I'll do the math for you again.

50/3 ~ 17

7.5(0.83)+8(0.17) = x
6.225+1.36 = x
7.585 = x

Still a small fluctuation and if you add plants or dose CO2, it will gradually lower again to 7.5 in time for another water change.

If you want to do biweekly water changes,

7.5(0.75)+8(0.25) = x
5.625+2 = x
7.625 = x

A tenth of a degree is an okay change, especially if you have plants to stabilize the pH.

 

[Masha]

Excellent! Thanks for all the helpful answers.

Too many variables here to really know what's going on!
I suspect Caliban is right about the gouramy and cory deaths maybe being caused by underfeeding so I'm trying to correct that.

I need to test PH just after doing a water change as well to find out how much of a PH change is happening.

It also occured to me that I could get my GH and KH tests done at the Two Oceans Aquarium, since I do volunteer work there every week. They mostly have marine tanks, but do have some freshwater fish there as well so surely they can help? Hope so.

I'm going to consider doing smaller, more frequent water changes in the mean time, until I have more of a grasp on what's causing fish deaths. If it really is only under-feeding, then all this is beside the point...

 

[icydeath]

Grab yourself some algae tabs and feed the cories at night. Feed the gourami in the morning or during day with some floaters so he doesn't have to root around for them.

 

[Caliban07]

Yes. Cory's love blood worm too. 1-2 times a week should be more than enough to supplement if you think they aren't getting enough food. The other way to do it is feed as normal on to of the water then take a small pinch in your fingers and crush the flakes up. Submerse your hand to the substrate and sprinkle near the Cory's. Only use a very small amount though. The Cory's should be able to sift through the substrate and find the food the others missed. You can also get some shrimp just to ease the worry of food getting caught in hard to reach places and rotting.


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[Masha]

Well, in the interests of accuracy, I did a 50% water change as usual today, and measured the PH afterwards. It's not such a big difference as I feared.

Tank PH before water change, = 7.5
Tapwater = a bit over 8 (the test doesn't have 8.5 on the scale, but the colour was somewhere between 8 and 9)
Tank water just after 50% water change = a bit over 7.5

So if that's accurate, there's not such a big swing in the PH after all, when I do that water change.

Caliban, I tried your method of leaving a pinch of flake food near the cories - I can see this is a skill I still have to master! The flakes went up instead of down

But what I generally do, is to float a crumbling of flakes on the one side of the tank and keep touching the water with a chopstick to keep the tetras interested in that area. While this is going on, I sink a tablet at the far side of the tank. Most of the time the cories get to the tablet first, and at least have a good nibble at it before the tetra-brigade realize what's going on.

I'm going to hope that it's the under-feeding that was causing the deaths, as well as the fact that I had the temperature a bit too low.

 

[Caliban07]

Yeh I didn't think the ph would fluctuate that much tbh. Buffering doesn't always mean raising ph btw. The type of buffers will try to dictate the ph of the water and hold it there so it seems that the balance of your tank water settles at 7.5.

Try holding the flakes under longer so that the absorb the water. They definitely should sink.


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