Cycled FW Tank Serious pH issue

[Matthew C.]

Hi...I have a newly cycled 30 gallon FW tank, and home to 4 juevinile emerald Cory's (largest one about 1" in length.)
I introduced them nto the tank on Sat. afternoon. (3/25)
Everything was fine on Sat.
Ammonia 0.0,pH 7.4, nitrite 0.0
Nitrate 0.0
Sunday feed them some algae food...1/2 tablet of a Hikari sinking wafer. All good.
Monday, another half..... all good.
Monday night started the roller coaster ride.
pH 7.3
Ammonia 0.0
Nitrite 0.0
Nitrate 160.
Did an immediate water change, although the fish looked fine....Added prime, and two capfuls of Tetra TTS. Also added two capfuls of Tetra water balance.
Tuesday morning, awoke to cloudy water and pH at 6.6 ammonia 0.0, nitrite 0.0 Nitrate 0.0. Did a water change to bring pH back up......To 6.9
This morning, pH is below 6..0 (yellow​ color on API test chart using drops) ammonia 0.0 nitrite 0.0 and nitrates 30.
I have crushed coral in my canister filter and have had so for almost a month. Can figure why the pH was good for so long, and then it crashes?? I haven't tested the gh or kh because the instructions seem so vague and I can't distinguish the different colors. What can I do to correct the problem....Some people say don't worry about pH others say fix it asap.

 

[Bert2oo1]

Hi...I have a newly cycled 30 gallon FW tank, and home to 4 juevinile emerald Cory's (largest one about 1" in length.)
I introduced them nto the tank on Sat. afternoon. (3/25)
Everything was fine on Sat.
Ammonia 0.0,pH 7.4, nitrite 0.0
Nitrate 0.0
Sunday feed them some algae food...1/2 tablet of a Hikari sinking wafer. All good.
Monday, another half..... all good.
Monday night started the roller coaster ride.
pH 7.3
Ammonia 0.0
Nitrite 0.0
Nitrate 160.
Did an immediate water change, although the fish looked fine....Added prime, and two capfuls of Tetra TTS. Also added two capfuls of Tetra water balance.
Tuesday morning, awoke to cloudy water and pH at 6.6 ammonia 0.0, nitrite 0.0 Nitrate 0.0. Did a water change to bring pH back up......To 6.9
This morning, pH is below 6..0 (yellow​ color on API test chart using drops) ammonia 0.0 nitrite 0.0 and nitrates 30.
I have crushed coral in my canister filter and have had so for almost a month. Can figure why the pH was good for so long, and then it crashes?? I haven't tested the gh or kh because the instructions seem so vague and I can't distinguish the different colors. What can I do to correct the problem....Some people say don't worry about pH others say fix it asap.

What do u have in the tank other than fish? To cause such a high ammonia/nitrate jump in such little time is almost impossible unless adding ammonia to the tank. I'm guessing the ph of your tap water is around 7.3? It shouldn't be able to swing from 7.3-6 so quickly without adding chemicals. Have you added anything to the aquarium other than food?

Do u have any decor in the tank? Rocks wood etc?

Do u have carbon in the filter?

 

[scottsheldrick]

Your ph swings will almost certainly be because your kh levels are below 4dkh. Ive used crushed coral in the past and it barely worked. There are a few things you can do (but dont add anything to quick coz itll also raise ph at the same time and cause a big swing thatll kill your fish). Try baking soda, kh up tabs or seachem alkaline buffer. A kh over 4 will keep your ph steady. If you have the api kh and gh test kit, it is very easy to distinguish the colour changes if you have good levels of each in the tank. Not sure why your nitrate is jumping so quick, check for left over food scraps - i had a hidden uneaten algae wafer that was playing havoc with my levels (mainly coz i only have a small 45L tank which is hard to maintain..)

 

[Matthew C.]

I have and am using crushed coral, the safest way to go in raising your ph. Allows for a gradual increase in ph as opposed to ph up or down, which can and will give ph swings which can be fatal to aquatic life.

 

[J.Mcpeak]

All I can think of is;
Could be to do with plants?
Is it well planted. Plant respiration during lights out releases Co2, which is well known to cause acidification.
Add an air stone to come on in line with the lights going off.
(And then off when the lights go on.....)
That's option 1.
Option 2,
Your water naturally has a low Kh, so the crushed coral takes a while to buffer the water of your recent water change.
To fix that, I'd use a Kh buffer powder (like they use in ponds)
Work out what you need by weight, mix it in before hand. Job done.
Kh buffer powder very easily mixes into water, it'll take less than a minute.