nitrate spike and ph plummet

[pufferfishi8]

just got my xmas test kit...boy was i in for a surprise!
i have a 20g with some brackish fish, i recently (3 weeks) disturbed the gravel and added new rocks (which passed the vinegar test) as well as added a lot of java moss and ferns. water changes (3 gallons) every week.
well, nitrites and ammonia are nil, while my nitrAtes are thru the roof(140ppm!) and my ph is down around 6.5...i've done 2 water changes and rinsed my bio sponge in the last 2 days, and the only change is my ph climbed up to around 6.8, still massive nitrates.
could the new rocks be leaching the water? the water contains salt (specific gravity 1.003), but i thought salt raised the ph. (the tap water here is about 7.2).
is it because the gravel was disturbed? (had to find an eel who has gone MIA), i did kick up alot of cloud.
maybe bio sponge was overwhelmed? it rinsed pretty brown, i hadnt rinsed it in some time.
thanks, any help appreciated.

 

[carpguy]

You said the nitrAtes are still through the roof… have they gone down at all? You might want to check your tap for nitrates. The nitrogen compounds are acidic and are probably what is driving your pH down. I think this is called "bio-acidification" if you want to try a search. Have you checked your KH? Your KH (carbonate hardness) acts as a buffer (neutralizes the acid), so if its low the pH can drop.

My KH is virtually nonexistent and my pH is very low. I have a little mesh bag with 4 tablespoons of crushed coral sitting in my filter to try to drive the KH up. Its a taken a week to get it from 0 to <2 degrees. Ideally I think it should be no lower than about 3-4 degrees. I think I'm going to try adding more. My pH has jumped from <6.2 to about 6.4 (can't read the damn colors ).

HTH

*If your KH is too low in the tank, check your tap. You may have used up your normally adequate buffer. If the tap is higher you can replenish with more frequent water changes without having to resort to additives. My tap is very soft.

 

[RTR]

Salt, sodium chloride, does not affect pH at all.

If your tank is supposed to be brackish, you should use marine mix, not sodium chloride, for your water. Brackish fish are from high pH, high mineral content water, which marine mix will provide..

Brackish fish, especially if they are puffers, are messy eaters. The nitrates you are reading are doubtless just the result of your feeding. This is harder to control with messy fish, but water changes with vacuuming should bring the nitrate levels down to a better level.

 

[Sumpin'fishy]

Maybe I'm mistaken because all my fish have been omnivorous cichlids, but if you have a nitrate problem, I'd do a minimum of 5 gallon changes per week on a 20 gal (25%). 3 gallons a week just doesn't cut it, IMO. And I would do larger till you got rid of this problem, I do weekly 50% water changes to my tank. I know it costs a bit with your marine mix you need to add to water, but that's the only thing I know to do to fix this. Gravel vac every week also, if you have messy eaters like I do, You should do larger water changes each week. I suggest 50 % changes till it gets under 40ppm nitrates. Once it gets down to a manageable level you plants should be able to help keep it that way. I never let mine get over 20ppm, but I understand that this isn't always feasable. Another benefit to water changes is KH being added back into your tank. With planted tanks you have to keep your KH up to stabilize pH, especially if using CO2. (actually all tanks need to keep KH at a decent level- for pH crash safety)

 

[wetmanNY]

Where do the nitrates come from? They're the end product of ammonia. (You know this stuff; you're just not sitting down and thinking it through logically.) The ammonia comes from fish metabolism-- and from decomposition of plants and feed. Cut down on the feed. Step up the siphoning of debris. Keep rinsing those filters. Keep up the water changes. Your nitrates will start to drop.

"Salt" is NaCl, it doesn't buffer the water. Doesn't affect the carbonate hardness because it doesn't have any carbonates. "Sea salt" has carbonates in it and helps buffer the water. Most important is some "crushed coral" aragonite.

Your brackish fish can't be happy about such a low pH. Alkaline conditions are as essential to brackish fishes as some salt.

But you'll be on the right track after reading these posts here...