pH issues - keeps wanting to drop

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Emory

Aquarium Advice Newbie
Joined
Jul 28, 2008
Messages
4
Hi guys,
I've been dealing with some health problems, and I think I've traced a multitude of problems back to a water chemistry issue.

This is a south / central american cichlid tank with a few other tropical semi-aggressive fish (gourami, silver dollars)

Before I started having problems, I'll admit I was seriously lax in my testing, so I can't provide any long-term history. The short-term goes like this: I bought some new fish and started having issues with fin and mouth fungus, changed the water and added MelaFix and aquarium salt. This prompted me to start testing again, so my only recent history of the tank is AFTER I started having problems.

When I went to test my water, I noticed a ridiculously low pH (measured with a meter) - in the mid 3's! I quickly did a large water change to bring it up into the 5's. At this point, I only had the meter, and my test kit for everything else was expired and not giving any readings.

My tap water tests at a pH of about 7.5

What generally happens is, I do a water change and the pH goes up a bit, then it slowly starts dropping. Since then I've done a series of water changes, and added baking soda and a half handful of powdered lime to try to get the buffering capacity up. Right now, the water tests as a hardness of 75, alkalinity of 40, and pH of 5.5. Earlier today, immediately after a water change, it was around 6.5. Obviously these swings are quite dangerous, but I'm worried my pH will get crazy low again and do serious damage to my fish.

I'm wondering what could be causing these drops? Today I removed a significant amount of gravel, and ran the gravel vac (something I admit I hadn't done in quite a while). I know a lot of organic waste in the tank can cause pH crashes, and there was certainly a lot of waste in there, but the pH still seems to be dropping even after the gravel removal, 40% water change, and vacuuming I performed today.

My tank decor consists of a few plastic ornaments from petsmart, some plastic plants, and two decent sized fellerstone carved rocks - one lava rock, and one "rainbow". The only thing relatively new in the tank is a Fluval 305 filter, but I doubt that could be leeching anything that's lowering my pH.

In addition to the Fluval, I've got two of the external hang-on-tank filters, one no-name brand and a small penguin biowheel. The tank was well established and cycled, but I'm pretty sure the ridiculously low pH killed off the bacteria. I've gotten a bit of gravel from the LFS to try to re-seed the bacteria, and am using Amquel+ with my water changes to try to keep ammonia low.

I'm at a loss, both about what could be causing the pH drop, as well as what to do about it. Your advice is greatly appreciated!!
 
My guess is that lax aquarium has led to sky high Nitrates which is causing the pH to drop. This is generally know as Old Tank Syndrome. While you do want to get things stabilized, you'll want to make sure that you don't do too large of water changes and shock your fish with too sudden a change.
 
I was lax with my water testing, but I was not lax with my tank maintenance. I changed the water regularly, and since I've started having problems the nitrates have consistently tested at 20 ppm or less.
 
In that case I'd test your source water. Could be that the water treatment changed without your realizing, so you are now dealing with water that basically has no buffer.
 
I did test my tap water for pH but haven't tested its hardness. I'll try that when I get home tonight. I did leave a cup of tap water sit out to check the stability of its pH, and it was pretty stable overnight.

In the meantime I've added small amounts of baking soda throughout the day to try to get some buffering capacity. The pH now sits a bit high for SA Cichlids (around 7.8 but I was more worried about the pH crashes. My plan is to do regular (twice daily, maybe more) small (~10-15%) water changes and monitor what happens to the pH. And obviously check the buffering capacity of my tap water.

If it turns out my tap has little buffering capacity, would it be reasonable to add some crushed coral to one of the filters? I'm worried that this would maintain the pH at a too-high level, but as I'm not breeding, I'd rather have stable pH than "ideal" pH.


I'm still at a loss as to what could be causing this.
 
You can adjust the KH/pH to a degree by controlling how much Crushed Coral you add.
 
The tap water tested a little over 8 today, so I have a feeling some of my issues may be due to fluctuations in the tap. I found out that there was a power outage at the treatment station last week and things got a little screwy. I'm also showing about 20ppm of nitrates coming out of the tap. Hardness and alkalinity are decent from the tap, but with the fluctuations we've been having it's possible they were crazy a few days ago.

I'll be closely monitoring my tank and keeping the water changes small. I'm pretty sure the pH crash killed off most of the bacteria in my filters, so I will have to keep a close eye on ammonia. The good news is - the pH is holding stable, albeit high, at 7.8. If it starts to drop again (when the baking soda is used up), I'll consider adding a bit of crushed coral to keep it steady.
 
I believe you've found your cause. Sounds like a good plan and you should be able to get everything back to normal soon.
 
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