Maintaining PH and KH value

[Shawn]

Dear all shifu,
I am facing a problem of low KH and PH value in my tank. And I know that PH drop fast is due to or part of reason of low KH.
Tank size 5 by 2.5 by 2.5 with sump tank 3 ft
Ammonia and nitrate lvl are both at zero which I believe my media is good enough to handle? (Correct me if I am wrong) I have use API KH test kit just 1 drop the water turn yellow straight away without traces of blue.
I had add a lot of coral chip in sump tank already but still can't keep ph at 6.5lvl. My PH is alway 5.5 - 6 lvl which I am scare of a PH crush.
I have tried to do more WC but PH value drop back again the very next day.
Anyway can I maintain my PH value? Adding more CC?? Or is it bio load too high that my media cant support?? commercial chemical solution will be very last solution to the problem.

Stock in tank:
1) Red Aro 18"
2) 4x IT 12"
3) 5 x bichirs 15" each

WC every 5 days 70%.

[DragonFireSG]

You will probably need to dose sodium bicarbonate to increase KH. An active bio filter constantly depletes carbonates, and it seems to me that the coral chips (calcium carbonate) does not dissolve fast enough to compensate.

[DragonFireSG]

Personally I prefer crushed oyster shell for calcium carbonate buffer. I think it is more soluble than coral chips.

[Oneiromancer]

Any sign of uneaten food in your tank/sump? Also, how often do you feed them and what are you feeding them?

[Shawn]

feeding only once a day on MP. I dun overfeed them so there shouldn't be any leftover food. at the moment I using KH solution to increase the hardness of the water in order to maintain the PH value. still trying to find a better way.

[DragonFireSG]

Try adding more aeration - specifically in the coral chip area to agitate the water and force more circulation through the chips. Try crushed oyster shell too for a change. You need more soluble carbonate media.

The 70% WC probably contributes as our source water in SG has very low carbonate content. That straight away dilutes the KH. Here's a thought. Consider aging your WC water in an aerated drum full of chips or oyster shell. That should harden up the water some.

[Oneiromancer]

Similar to the above post,I think I was once able to increase my pH a bit by increasing the aeration. It increased the pH by 0.5 (thereabouts). However, in the long run, you may want to put more coral chips in a laundry bag and add to the area with the most water flow. Then monitor and adjust accordingly.

How are your fishes though? Are they healthy and eating well? I personally belong to the school of thought that large swings are more deadly than low pH. The greatest concern for low pH, for me at least, would be the lack of beneficial bacteria, as they are unable to thrive under low pH.

[Shawn]

thanks all bros for recommendation,
at PH 6.5 - 7 my fish is happy and eating well but when it hit below 6 they do not want to eat and tend to stay at the same spot. so when I see my fish behaviour like that more or less I know is the PH that causes it. I also scare my BB cant make it at those PH 5+. I always test for ammonia and nitrate lvl when their behaviour change.

I place my cc at my last section of my sump together with the returing pump.
all other section is full with my media already. hahaha

[DragonFireSG]

One interesting thing for consideration.

Beneficial bacterial require carbonates to thrive. When they eat up all the carbonates, PH becomes prone to shifts. When PH drops too low, the BB die off. Vicious cycle that can end very badly.

KH imo is one of the most important water parameters to keep an eye on for us water keepers. We keep the water. The fish will keep themselves.

[Oneiromancer]

TS any update? Anyway I put a laundry bag packed with CC in the tank itself previously.