Default Nitrate Levels Options

[CP]

I am talking bio tanks here.

Frankly,I have not bothered about nitrate levels for the past year since I took up this hobby.My stock level is low (750l for 9 fishes),I do 30% water changes forthnightly,the fishes growing well and no diseases (touch wood) so far.

Until I chance upon RafflesGold forum.After browsing thru the old threads and subscribe to the advice of keeping nitrate levels below 50ppm,got myself a Tetra test kit 3 wks ago and... WAH PIANG!!Turned red in no time!Performed 80% water change immediately and still red!Performed another change and brought down to abt 25.

Whew,I thot,the level must have been in the hundreds to begin with.After the first week I find that I need to perform at least 50% change weekly at the current stock and feeding level to keep it below 50.

Now-straight to the point.I found that when I did 80% change (lazy to net fish out la) at 50ppm I was expecting nitrates to be abt 10 (0.2x50=10)afterwards but found that its abt 25.After the next water change (same parameters) also discovered abt 25.The maths don't tally.So I tested tap water - wtf already 12.5!Checked PUB website and found that nitrates in tap water can be up to 15ppm.

There you have it - After water change 10.
Tap water 12.5

The rest?In my opinion from the ammonia freed from chloramines (chloramine = ammonia + chlorine) after adding the water conditioner which was subsequently coverted to nitrates as well.I reckon it can be abt 2ppm judging from the recommended chlorine residual level from PUB website.

Therefore I conclude that even after you change 100% of water,the default nitrate level shd be abt 15ppm.You may think that I am mad for dwelling into these figures but after browsing the old threads I take comfort that there is a self- proclaimed nut case who keeps the nitrates levels below 40(or is it 20,I cant remember.)

That's all.Time to change water.

[CP]

The experiments carried over the weekend got me labelled a madman by my wife and Professer Utonium of Powerpuff girls by my kids.

OK,here's what happened:

Went to Cheers,got a bottle of 500ml Evian (wtf almost 2 bucks,I could have gotten myself a can of cheap beer ) but read the contents that nitrates are 3,8.
Not 3.8 but 3,8.Wonder what that meant.
So I browsed around and obtained another sample - a 500ml 'Life' pure distilled drinking water(why the heck would anyone drink distilled water) for 1 buck.The nutritional info were all listed as zero with no mention of nitrates.

And the results - Tap water (I tested twice) still 12.5
Evian - A shade below orange so I reckon its abt 8 to 10.
Life - Yellow!Not bright yellow,but my guess is 1 or 2.

This was followed by an 80% change of tank water at 50ppm and as expected the result was abt 25ppm (0.2x50 + 12.5).

Conclusion:
For my 750l tank performing 100% water change,I have the option of using PUB water costing abt $1.50 inclusive of water borne fee and water conservation tax
and obtain 12.5ppm nitrates; or I can purchase 1,500 bottles of LIFE costing abt 1.5k and obtain almost zero level nitrates.