Hi there,

This week I decided to set up the new Juwel 400ltr tank I have had sitting in storage for the last couple of months to move my ever growing bunch of cichlids in to.

I washed it out with plain water, set up the heater and filter per the instructions and added a whole lot of rainwater (my usual supply - filtered tank water as we live rurally). Before doing so, I washed (in plain water again) and added my chosen substrate - black coarse sand purchased off TM, mixed in with some white aragonite sand (also purchased from the same supplier).

I have tested the water for 2 days running and the ph is 9.5+ (I say + because my test kit maxes out at 9.5 and for all I know it could actually be higher!)

Before I purchased the substrate, I got the guy to send me some samples and I did a test on it with my rain water. With just the black substrate, the water had quite a low ph as it is not really a buffering agent, so I added some aragonite sand to get a "salt and pepper" mix (about 4 parts black sand to 1 part aragonite sand) and this created the correct ph of 7.5 - 8.

I have mimicked the same ratio in the big tank and am at a loss as to why the ph is off the chart. In my other two cichlid tanks where I use the aragonite sand only, the ph is 7.5 - 8.

Could it be something other than the substrate or in a brand new tank is that all it could be? Any helpful suggestions would be appreciated!

Question (for clarification):

You say that you have tested the water for 2 days running and the ph is 9.5+, have you changed any water?

What I would do in this situation would be to perform some large waterchanges, syphoning the water through the substrate.

Obviously there are no livestock in the aquarium so big temperature and ph swings aren't a concern.

9.5+ wow im no pro, but have you tested the water your using aswell before adding it to the tank, and adding drift wood helps too, other then that the more experienced guys would be more helpful

That PH seems very high with the amount of buffering you've described.

Waterchange and retest. Test also your water supply, if you're on tank water and it is low it may have risen. Also if you have bought water lately as Bore water is usually very hard.

It probably should settle with time.

my $ would be on the test kit being faulty, how old is it?

Here's a theory - the samples were pure aragonite and tested fine. The larger quanities also contained a whole pile of aragonite dust, which has disolved into your water, causing a temporary rise in pH. Do a big (90%) water change to flush it out, and see if the pH drops. If it does, you know it was a one-off and you don't need to worry. If it doesn't, test water from another tank to verify the accuracy (or otherwise) of your test kit.

Ok this is weird! I didn't test the water before I added it to the tank as I filled a new tank before christmas, tested it then and the water was a nice neutral 7.0. I also use this water supply each week to do 15% water changes on my 2 fish tanks and the ph of the tanks has remained steady and the fish have been fine.

The water source is a friends down the road - rainwater collected from the roof of her house that is stored in a concrete tank. We are on filtered irrigation water which is why I use her water as I didn't think the fish would like the irrigation water.

I tested the water at source and found that it now has a ph of 9.5+. I went to another friends house about 7km away to get alternative tank water and what do you know, her water is the same high ph.

I have two test kits and used them both to test the water - both gave the same high ph readings. I then came home and re-tested my 2 fish tanks and they both have a ph of 7.8 (just where I want it!) and our filtered irrigation water has a ph of 6.5 so I guess the test kits are just fine. My two fish tanks both have 100% aragonite sand in them to help keep the ph stable.

I don't understand what is causing the ph to be so high in both concrete tanks. We haven't had a good downpour here for a while - would the ph of the water increase the longer it sits in the concrete tanks? If so, I will need to watch out for this in the future.

Right now, I am thinking a 50% water change replacing what I take out with filtered irrigation water might be the way to go. What do you think? Does anyone else use filtered irrigation water in their fish tanks?

This is so weird - if anyone has any theories on why our rainwater has suddenly spiked from a ph of 7.0 to 9.5+, I would really like to hear them! :roll:

Concrete raises the pH.

water change and re test it

the aragonite will spike up your ph anyways but like you said it isnt that much.

so it must be something else

test the tap water.... but 9.5 seems highly unusual and definatley not normal

my tap water here in albany auckland is about 7

drift wood would definatley bring down the ph but there is a problem here, maybe your test kit is faulty.... get anew one?

I used to use rainwater but found it to be far too variable to be any use. It had wildly swing pH (but not as high as yours) and would change it's characteristic depending on which way the wind was blowing when it rained. Rain can be quite dirty - by that I mean have many dissolved chemicals in it from industrial pollutants. Maybe wait until it rains next and see if the next water is better. Of course, where you live there may not be airborne contaminants. Looks for some reason for it to change. How far are you from the nearest city or industry of any kind???

Testing your friends water could be a good idea - as caryl has said above, concrete can raise the ph of the water. How new/old is the concrete tank you got the water from? the newer the concrete, the more likely it is to raise the ph.