Need math help with cycling

[AZBigJohn]

I need math help tonight...

I am cycling a 155 gallon tank, with a total water volume of probably 150 gallons all told (155 gallon tank, with a 55 gallon sump, with a total of 30 gallons of water in it, minus 160 pound of rock).

So, I have been unable to get ammonia over 1 ppm with my two dead and decaying shrimp for over a week, and I really want to challenge my rock. I started with 100 pounds of base rock and 60 pounds of cured live rock.

So I went out and bought the professional strength ammonia from Ace Hardware everyone recommends, with nothing but pure ammonia in it (no surfactants). Says it contains 10% Ammonium Hydroxide.



How much do I need to add to get my 150 gallons of water from .75 ppm to say 2.5 ppm?

I am usually very good at math, but for some reason, it just will not compute for me today...

 

[disc1]

If you have 150 gallons then that's 150 * 3.8 = 570 Liters.

So to raise ammonia by 1ppm you'd have to add 570mg of ammonia.

Your bottle is 10% ammonium hydroxide and NH4OH is roughly 50% ammonia by weight.

So let's call that bottle 5% ammonia, meaning 50mg / ml.

So it looks like about 11ml of that solution to bring ammonia up by 1ppm.

If you want to go from 0.75 to 2.5 that's a bump of 1.75ppm, so you'd use 1.75 * 11 =

19.25 mL.

 

[AZBigJohn]

Thank you very much, David. It was the Ammonium hydroxide that was throwing me off, I had no idea what that did to the equation, and I was toast from there on...

 

[dkeller_nc]

Hmm - I'd be really cautious about dosing the ammonia. If your tank was all dry rock, an overdose wouldn't make much if any difference. However, since you mention that you've got 60 lbs of cured live rock in the tank, I would at least spread your dose out over a day or so.

Depending on how "live" your cured live rock is, you could conceivably kill some macro-life on the rock, such as sponges, tube worms, etc..., and that might not be desirable since I infer that you're trying to get the life in that rock to "seed" the dry rock.

If your 60 lbs of cured live rock had a lot of life on/in it, that would explain why there's little ammonia in the tank despite the presence of two rotting shrimp.

 

[Reefsi]

A spike of 1ppm ammonia would be considered normal, especially with using that much cured live rock already. Even if you bump it to 2.5ppm some of that bacteria will just end up dead anyhow. The amount of bacteria is determined by your bioload. So unless your always adding that much ammonia then its pointless. Your system will adjust to your bioload, cycling a tank is a term to just establish bacteria in your tank, it will then multiply or die off accordingly to what nutrients are available in your tank.