Water chemistry wierdness

[Karen]

I will preface this by saying... everyone is healthy, there are NO problems.  This is a well established trend and not anything new, but I can't explain it.  All 4 tanks have nitrates under 10ppm following their weekly water change.

Four tanks, 2 with good pH, KH and GH and 2 with really low pH, KH, and GH.  How low you ask?  Not sure, my tests aren't sensitive to answer the question!!!

The "normal tanks" are
125 gallon- lots of drift wood- pea gravel from Agway for a substrate.  Many decorative rocks.
70 gallon- lots of drift wood- aquarium gravel that has been in use at least 15 years. Lots of rocks in here too.(This tank is unheated.)
pH 7.2
KH 4 drops
GH 5 drops


The low tanks are
210 gallon- lots of drift wood- aquarium gravel that has been in use at least 10 years.  Lots of rocks.
30 gallon tank- no drift wood, no rocks, substrate is 1/2 new gravel (less than a year) and 1/2 aquarium sand also newish.
pH- the lowest my kit will read is 6.0, the tanks might be lower, not sure.
KH-the color does not change, the first drop has the reaction in it.
GH- I think the color changes on the 2nd drop, but it may be in the first.


The rocks used in the 3 tanks are all interchanged and moved around regularly to allow the plecos a chance to clean them off.  Drift wood moves around too with the exception of a MONSTER piece in the 210 that I am not going to move.  I can think of nothing that the 2 pairs of tanks have in common.

Like I said, this is a long established pattern with no obvious ill effects, clearly I am just looking for things to worry about here.  Any one got any thoughts??

[Shaner]

i m assuming you have well water? if so, is there a possiblity that if you drain and refill your first tanks, that they are using so much water that it might actually move into a differant part of the water table??? which could have the differant parameters? I know I am stretching, but if you have eliminated everything in the actual tanks, there should be no other reason for the changes. Could it be the fish themselves that are changing it. their waste or something. What about the types of glass between the tanks, I know you repaired the one, differant chemical composition??

I dont know sounds weird, but if all the fish are happy and healthy then good.

 this could be the million dollar question, very interesting, I will be curious to see what others might think,

another thought how close are you to the ocean, maybe that might have something to do with it, some hidden tunnel or something that when you fill your tanks the tide changes and the moon rises and maybe there is some treasure in that tunnel too. hmmmm could be a pirate's booty 

seriously though very interesting, will be neat to see what others come up with.

[Karen]

No well here, this is town water.  I am about 25 files from the ocean.

I hadn't thought to blame pirates.  Is this the work of the almighty FSM perhaps?
 

[Shaner]

hmm, no well, city water, and 25 miles from the ocean.......

are you tracking the rocks into the tanks when you move them around? maybe there is something to the mineral content of a certain combination of rocks that when you get the right combination it changes the water??

[Belinda]

You have very soft water there ...
 the numbers do sound odd..
the larger tanks would be the most stable naturally ..

 I would be afraid of those tanks "crashing" ..

just the act of nitrification would lower your KH .. that could be part of the reason for the lower numbers in those tanks ... they are the ones with the heaviest bioload in them ..

I would want to add some crushed shell sand , Argonite or something like texas Holey rock to your tanks to increase your GH and Kh a little bit ...
Just a suggestion ...
 there is a saying ..."If it ain't broke , don't fix it."
You are lucky that they stay stable for you......

Maybe somebody else has an idea.
 

[gomezaddams]

Thats my only thought.Somethings "eating" the gh and kh.
The pacu I could understand the amount of waste they produce,the nitrification eating up the kh . but your nitrates are low.odd.Id have to say its the driftwood.
the 30 has young growing fish that could use up minerals faster too.maybe.