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ph drop over night

soggybongo

soggybongo

Member
Joined
5 Aug 2018
Messages
243
Location
Bradford
hi guys a little confused as to whats going on with the ph in my planted tank and also water change tank.

tested both tanks last night befor going to bed and both reading ph 7.0

got up this morning and before the wife and kids get up i thought i'll get on with the first water change but before doing that i wanted a ph reading of both tanks to ensure they are the same before going ahead.

planted tank reads ph 5.8
water change tank reads ph 6.4

i dont know why it has dropped like this over night

i'm using ro water and buffering/ minerising with equilibrium.

no livestock in main tank, co2 turned off at 8pm last night and light off at 9pm.

my first thought was maybe the substrate is pulling the ph down but my water change tank has lowered also so this rules that out.

checked calibration of my hanna 9124 ph meter with ph7 and ph4 solution and both were spot on

any thoughts?
 
I'm really no expert in the science side of things but as I've spotted your post... I believe plants release CO2 during the night. Is your tank very heavily planted. This action plus the soil may account for it?
 
hi matt, yes but still doent explain my water change tank lowering as all thats in that tank is a circulation pump and heater
 
ive changed the circulation pump in main tank this morning as the fluval pump the tank came with is only 500lph so now installed a eheim 1048 extra 100lph flow so i can create more surface aggitation whilst still having good all round flow
 
I'm stumped... someone with a better chemistry brain is required on this one! I try and stay out of this side of the hobby... at some point they'll offer a degree in aquascaping I swear it can get complicated if you want it to. I like the simple approach!
 
tested my main tank water for gh and kh
gh = 4
kh = 1
temp 22.5c
drop checker with co2 on was green during co2 and light period but did start to turn a lime green but not quite yellow just before co2 off.
light were set to 100% 12 on 12 off during dry start method but since flooding lights set to 40% 6 on 18 off.
co2 comes on 2hr before lights on and co2 goes off 1 hr berore lights off
 
Hi all,
soggybongo said:
checked calibration of my hanna 9124 ph meter with ph7 and ph4 solution and both were spot on
Click to expand...
That is a good quality pH meter, so the pH values are likely to be right.

The pH changes could be to do with changes in the dissolved gas pressures in the water, but because you are using RO that is more unlikely.

It is probably back to the low carbonate hardness of the water, it only needs very small changes in water chemistry to lower the pH. The fluctuating pH honestly isn't an issue, it is an inherent property of very soft water.

cheers Darrel
 
im going to bring my gh in water change tank from 4 to 6 let it run for a few hour and do the water change to see if that makes any difference to the ph over night tonight and test again in the morning
 
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