PH down suddenly from 7.6 to 5.2!

[Keith024]

Hey guys,

I need your help again :(

I am in the 17th day of a fishless cycle (using Ammonia) and suddenly the PH has gone down from 7.6 to 5.2!

This has left me baffled, I dont know why this has happened, anyone can help please?

Water parameters:

PH: 5.2 (gone down)
Ammonia:0.25 - 0.5ppm (gone down)
Nitrites: 0 - 0.25ppm (stable)
Nitrates: 40PPM (gone up)
TDS: 276ppm (going up)

103735

[DJW]

The nitrifying bacteria have consumed all of the carbonate hardness (buffer) in your water and made it acidic. If you measure the KH there won't be any.

You just need to change the water. Then the pH will go back up and the beneficial bacteria will start working again. If you use less RO and more tap water the pH will stay stable longer.

The rule of thumb is that for every increase in nitrate of 11 ppm, 1 dKH of carbonate hardness is destroyed. When the KH reaches 0, the pH crashes. This rule only applies to fishless cycling with ammonium chloride (Dr. Tim's etc). When you are using the cleaning ammonia the pH will be stable a little longer because it adds alkalinity along the way.

[Keith024]

DJW

Many thanks for your reply. So this is something I should worry about only now that I do not have fish in the tank? is that right?

So if I do water changes more frequently it should keep the KH and PH stable right?

The only issue I have (and I predicted this but I cant really do much about it because I dont have space for a bigger water storage tank) is that due to the size of the storage tank I can only do a 25 to 30% water change at a time.

The other issue is that tap water here is very high in nitrates so most Discus keepers avoid using it. :/

[DJW]

With fish in the tank you would normally be changing water often enough that the pH stays stable. A big drop in pH like this is much more likely to happen during fishless cycling because it doesn't look like water changes are needed.

If you are forced to use 100% RO water because of nitrate, you might have to add buffer to the water. What is the KH of your tap water, and of your RO water? If I remember right your RO water still had a TDS around 80 ppm, so it might have some buffer left in it.

Your tap water is like mine... not good for much. I use 100% RO and only need to add buffer for the rare occasions when I won't be able to change any water for 2 or 3 days.

With juvenile discus you really need to be able to do 50% water changes, and even with adults there will be times when you want to change at least that much at a time. Can you get a bigger barrel and put it in a closet maybe?

[Filip]

if i would have to choose between doing only 30 % WC with RO water or doing 60%Wc with half tap half RO , i would choose the second IIWY .
Remember that WC is not used just for stripping nitrates from water column. Bacterial count , pathogens and many other unmeasurables are far more important reason for doing WCs.

[Neptune]

if i would have to choose between doing only 30 % WC with RO water or doing 60%Wc with half tap half RO , i would choose the second IIWY .
Remember that WC is not used just for stripping nitrates from water column. Bacterial count , pathogens and many other unmeasurables are far more important reason for doing WCs.

and restoring calcium and magnesium ions for proper ORP reactions

[DJW]

if i would have to choose between doing only 30 % WC with RO water or doing 60%Wc with half tap half RO , i would choose the second IIWY .
Remember that WC is not used just for stripping nitrates from water column. Bacterial count , pathogens and many other unmeasurables are far more important reason for doing WCs.

Agreed. Whether to use RO, or how much to use, is a judgment call you have to make considering the cost of your water and how much nitrate you have from the tap. If I had only 10 ppm nitrate and the water was otherwise fine, I would probably just use the tap water.

I think the OP is limited not so much by the amount of RO being produced, but by space for a bigger storage tank.

[Keith024]

I have tap water at nitrates - 40PPM or more and between 600 to 800 PPM TDS I do not drink tap water and if it is not good for me it is not good for my fish I think :/

I will now try and another storage tank but the missus wont be happy even though it is in the back balcony which we only use for drying clothes etc... ;)

Yes I add Priess Discus minerals to the RO water however the TDS are considerably high even though I am not always adding in these minerals at the moment after a 30% water change it was around 246PPM TDS.

RO Water without added minerals is 80 PPM TDS.