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Help with gH and kH tests


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I bought the API testing kit and tested both aquarium water and tap. I'm a little confused!

Tap: gH 71.6 ppm (4 drops), kH 125.3 ppm (7 drops)

Tank: gH and kH both 89.5 ppm (5 drops ea)

Is it normal for one to go up and the other down? Also I'm having trouble with the subjective term "bright yellow". Out of the tap it was what I'd call "pale" blue, but turned pale green, then pale yellow, but not what I'd call "bright" yellow for a cpl more drops. Out of tank it was never blue at all. I read the article on it and am still confused. Pale and bright are somewhat subjective terms and I want to make sure I'm measuring correctly. My fish will be harlequin rasboras, pearl gouramis and corydoras paleatus.  

pH out of the tap is about 6.8, after two weeks aged it falls to 6.6, in aquarium with driftwood it's 6.4. Still fishless cycling, ammonia 1-2ppm, NO2 just barely over 0, NO3 40+. Thanks for any advice!

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Over time, the tank will consume KH as it buffers the water. 

And yes, the color vividness of the API tests can be subjective. I find the difference between 20 & 40 on the nitrate test very hard to discern for my aging eyes. I also find the colors on the high Ph tests difficult to differentiate (7.4 Ph and 8.0 ph look too similar to me). For your purposes, i think as long as you're within a drop or so of certainty of the GH/KH reading you're fine. 

I'm not sure what's contributing to the GH, could be rocks or other hardscape possibly, but that's such a small bump I'd not worry. Just track it's trend over time so you know what to expect from it as your tank settles in.

Same with KH, track its trend a bit until you get a good idea of when, and if, the tank depletes it. 5 KH is a good amount to buffer your aquarium. With normal water changes you shouldn't have problems. You just want to make sure it doesn't go below 1. 

If you're shooting for specific values in terms of GH/KH/Ph, then you'll have to muck around with adding buffers and minerals to the water, things like crushed coral or Seachem equilibrium or alkaline buffer, but I don't believe that's your objective, and that costs money and time and usually isn't necessary except in very specific circumstances. 

It's normal for things like driftwood, CO2, fish waste to swing Ph down gradually as that acidifies the water. You just want to avoid it bottoming out or it changing suddenly (which is what KH is supposed to buffer against).

I won't claim to be an expert on any of the above, but I've did a bunch of reading on this over the past year or so trying to wrap my mind around GH/KH/Ph, how it changes over time and what changes it, so I hope my advice is good.

Usually if I get a new tank setup, I'll test it frequently and keep a mental trend-line things like KH and PH and nitrates so I get a good idea of how things work over time so I know how frequently to water change, etc. Then I test far less often once I'm confident how the environment works and the tank appears healthy. 


Edited by tolstoy21
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Thank you! Yes, I have several rocks in the tank (CaribSea Exotica). I also have a little trouble with the color change on the nitrates (same reason). I'm not shooting for a specific water hardness/pH as I am new to the hobby, just want to make sure what I have is in the comfortable range for my soon-to-be fish. I plan on doing a 15-20% water change weekly (45 gal tank) to keep the numbers from swinging too much. I really appreciate your detailed response! 

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No problem.

I think the best advice I've seen I've seen in this hobby is to not stress over all the above things. (Of course when i first got into this, I didn't take that advice and did the opposite to no avail). So just keep your parameters in the ballpark for a healthy tank without chasing specific parameters. 

Figure out what your water is like, and how your tank trends over time, and stock fish that like that your water. Most fish do well in a wide range of stable conditions. This is the simplest thing to do, and the easiest path to success.

Of course, on the flip side, some fish prefer and thrive in a higher Ph (alkaline) and others thrive in  a lower one (acidic). If, and when, you get into keeping those fish that don't naturally thrive your tap water, then you'll need to start thinking about buffering your water differently to accommodate those species. But that's fun for another day!

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