Very Low Kh

[Themuleous]

Hi people,

Did my tank testing last night and my middle tank had a KH of bearly 1, so did a 50% water change with 100% RO water and extra Kent RO Right, to try and get it up a bit. Retested today and its less than before!

I popped to tesco and got some baking soda, and have increased it to 2/3, but was wondering what could be causing it in the long term? I dont do anything to this tank that I don't do to my others, and they all have KH around 3/4.

I have read that nitrate creates nitric acid in the aqaurium, my nitrate is over 80? Could this be the cause? I also have two pieces of bogwood in there too. pH is around 6.5ish.

The trouble is that the KH seems to be getting lower, i.e. its actually being removed by something, any ideas? The onyl plants are some very poor looking polysperma.

I am aware this is not strictly a plant question, but as was quite rightly pointed out over in the emergency forum, you guys seem to have a good understanding of aquarium water chemistry, so hope you can help?

Thanks

Sam

 

[paulf]

Why not cut it with tapwater? will be a lot cheaper, what are the tapwater stats?

I tried some of the buffers, my tapwater is perfect for rifty fish and I now cut tapwater with ro for discus, buffers are a bit of a waste of time imo

 

[George Farmer]

I used to use 100% RO and add Kent's RO Right and pH Stable.

In short it was a test kit nightmare. There's insuffient Ca and Mg salts present in the powders to register an appropiate reading, even though the TDS may be ok you won't be able to test accurately using standard GH/KH kits.

If you insist on using 100% RO then personally I'd "build my own" water. Use Calcium sulphate and Magensium sulphate (3:1 I think) to build GH and Sodium bicarbonate (baking soda) to build KH.

I'm not 100% certain on the GH/KH building dosages so you'll need to research that a bit.

Then you'll only need to dose trace, and your other macros (NPK) to get the water you need.

Or you could just mix with tap to acheive the required hardness. It is a simple ratio i.e. if your tap is GH 12, KH 7 and you mix 50:50 RO/tap then you'll get GH 6, KH 3.5. This is exactly what I do. You also get the benefits of any extra nutrients in your tap water.

 

[iggy01]

I have read that nitrate creates nitric acid in the aqaurium, my nitrate is over 80? Could this be the cause?

It's certainly a possibility. Any acid, other than carbonic acid, will eat into the KH.

It would be a good idea to reduce your nitrate level via water changes.

Good luck!

 

[George Farmer]

I have read that nitrate creates nitric acid in the aqaurium, my nitrate is over 80? Could this be the cause?

It's certainly a possibility. Any acid, other than carbonic acid, will eat into the KH.

It would be a good idea to reduce your nitrate level via water changes.

Good luck!

I agree with Iggy.

Sorry, I got a little carried away with re-building RO for some reason and forgot to comment on the NO3 issues.

On the chemistry aspect, low KH can be a symptom of high NO3. If the NO3 is a result of nitryfying bacteria (and not KNO3 or tap) then this will likely cause a reduction in KH due to the acidifying properties of decomposing matter. This is commonly associated with old tanks, especially with undergravel filtration.

On the health aspect, 80ppm NO3 is certainly too high for any fish tank. Levels over 30ppm are well documented to cause potential health issues in fish and so lowering the NO3 should be a priority for this reason alone.

What is your current water changing routine? Is your tap loaded with NO3? I'm assuming you're not overstocked or overfeeding.

 

[Themuleous]

Thanks for the advice people,

On the RO water front, Ive just run out of RO right and looking at the prices of even small bottles its making me think twice about keeping on using it, especially as I have three tanks now (although granted they are not massive, yet anyway ) So think i'll give the tap water/RO water mix a try prob save me a fortune! (that'll mean I can afford more stuff, mwahhhh! )

I'm gonna work on getting the NO3 down, I'll have to use a pilow probably, until I start on the plants in that tank anyway. Will see how it goes. I don't think Im over stocked, but I may be near my limit. Thats the trouble with living near the gold fish bowl in Oxford, they always have such cool stuff in! And Barry (the shop owner) makes a point of showing me everytime I go in! No excuse thou I know. Although I didn't realise that over 30ppm NO3 was that bad, I have read very mixed things out how high it should be etc. Guess bringing it down cant hurt if it doesn't do any good! And I definately dont over feed, they only get two feeds as it is because I cant get home at lunch time.

My current water change regime is 25% each week, last time I checked my tap water NO3 was around 40ish I think, not at home so cant check my chart (Im sad like that, have charts and everything! )). The PO4 is also around 2ppm, thats partly why ive hesitate to add tap water to my RO water.

I guess my biggest problem is that I cant go the whole hog with the plants in this tank, im many ways it would sort a lot of my troubles out!

Thanks again people, always good to have friendly ears (or should that be eyes?) to ask for advice

Sam

PS George, so its not the NO3 itself that lowers the KH but the process of the bacteria breaking down organic matter and making the NO3?

S

 

[George Farmer]

George, so its not the NO3 itself that lowers the KH but the process of the bacteria breaking down organic matter and making the NO3?

You've got it .