Somethings Not Right

[eaglesaquarium]

Sounds to me as though your water has extremely low buffering capability.  The crushed coral you'd been adding to the filter was maintaining that buffering capacity, but without it... the water does it's 'natural' thing which is the formation of nitric acid (nitrate) as the end result of the nitrogen cycle.  When that nitric acid builds up, it slowly erodes whatever buffering capacity is in your water quickly causing a pH crash.  (More nitric acid is produced all the time and once the buffering capacity of the water is reached the pH starts dropping.)
 
 
I don't think that anything is 'wrong'.  That's just your water chemistry.  The phosphate remover might be removing some of the buffering ability as well.  Personally, I'd just keep adding the crushed coral as you have been... and make sure to ever remove it for an extended period of time.  Oh... and be sure to replace it as necessary.
 
 
As for the fry tank... I'd add a smaller amount of crushed coral to that, so that the water parameters in the two tanks are as close as possible.

 

[Akasha72]

I know my gH and kH are both around zero - one so no nutrients. I think my first mistake was listening to advice on adding leaves and cones without doing some serious research first. With the main tank I'm just gonna monitor for the next couple of days and water change if it drops below 5 again. The fry tank has been water changed today and the pH is back up to around 6.5. The leaves have been removed and so I'll monitor there too and again - water change if I see the pH drop too low.
 
I've now run out of coral and so I need to go and find some more somewhere so I can add some more to the filter for the main tank and be ready to add some to my fry tank if I can't keep that stable

 

[eaglesaquarium]

Leaves and cones have their place, but they do soften and they do also lower pH as a result as well.  For most folks, the effect is minute, but when you are dealing with nearly no buffering capacity, then the effect will be far more significant as you can see.  And that's why all advice needs to be double checked, because no one knows your situation better than you do.  

 

[Akasha72]

indeed. I'll think twice in future 

I just hope I've not done any un-seeable damage to my fishy friends

 

[Far_King]

The important thing is you got to the bottom of it and now know it can be an issue.  Will you be going back to using the red bush tea?

 

[Akasha72]

yes, as I've found that to be the issue ... if I find that it is causing an issue I'll stop that too

 

[Akasha72]

okay, so the water I set aside yesterday (from the tap) reads this morning as pH 6.5 which explains why my tank runs normally at 6.5 (or did) My fry tank pH reads this morning as around 6 - that's not moved much from yesterday. But I'm worried my main tank is in the process of crashing again. It's got a pH between 4.5 and 5
 
I have an appointment this morning but once I'm home later I'll be doing another water change on the main tank. I also need to go and see if I can get some more crushed coral from somewhere, maidenhead aquatics may have some and I need cory food too so I'll have a trip out to them 

 

[Akasha72]

pH is below 5 again ... *sigh* this is getting on my nerves now

 

[eaglesaquarium]

pH is below 5 again ... *sigh* this is getting on my nerves now

 
Have you added the crushed coral back into the tank yet?   If not, then you aren't going to be able to keep the pH up... you need a buffer in the water to stabilize the parameters.

 

[Akasha72]

the coral is back in my filters with a bit extra added (all I had left). I can't understand why it's not keeping itself up 

 

[eaglesaquarium]

the coral is back in my filters with a bit extra added (all I had left). I can't understand why it's not keeping itself up 

 
Time.   If I remember correctly, you mentioned you were doing a significant amount of water changes still.  Every time you water change right now, you are taking out the buffering chemicals from the tank.  It will take some time to get back to where it was.
 
 
 
Get back to your regular routine (what you were doing before you noticed the pH drop) and monitor.  Believe it or not, water changing at this time is not going to help things... on the contrary they will undo the buffering process you are looking to rebuild.

 

[Akasha72]

I wish I'd seen your reply earlier, I've changed a further 50 litres today. I'll leave it now though and see what happens. I've not said it before but I really appreciate your help, it's been good to know I'm not alone with this, it's stressing me out and so knowing there's someone here advising has been a massive help. When it comes to anything scientific I'm hopeless 

 

[eaglesaquarium]

No worries.  I love science.

 

[RCA]

don't worry, we comment on so much it's not surprising we get muddled, I know I do.
 
I've just got some new stuff for the phosphate problem - it's still aluminium based pellets but a different brand that's more economical (well it is on paper, not tested it enough yet) It's by Continuum and is called captiv-phos W. This is it's first time in my filters. I was using one by NTLabs but it was becoming expensive and so when I found this stuff was only slightly more in money (NTLabs was £15 and this new one was £20) for a pot three times the size I decided to try it.

Interesting topic, but sorry you are having these issues. I have not heard of the use of crushed coral before, where do you get this from and does it need changing regulary or just stays put?

In respect to the product quoted, I see this is a marine product, is that right? Again, what made you decide to include this in your aquarium please?

 

[Far_King]

 

don't worry, we comment on so much it's not surprising we get muddled, I know I do.
 
I've just got some new stuff for the phosphate problem - it's still aluminium based pellets but a different brand that's more economical (well it is on paper, not tested it enough yet) It's by Continuum and is called captiv-phos W. This is it's first time in my filters. I was using one by NTLabs but it was becoming expensive and so when I found this stuff was only slightly more in money (NTLabs was £15 and this new one was £20) for a pot three times the size I decided to try it.

Interesting topic, but sorry you are having these issues. I have not heard of the use of crushed coral before, where do you get this from and does it need changing regulary or just stays put?
 

 
Information on the coral as per my first post

 
http/www.fishchannel.com/fish-health/the-role-of-ph-and-the-nitrogen-cycle.aspx