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I suspect there is no straight forward answer to this question but I am seeing some Ammonia build up in a small 45 gallon 1:1 system that's been running tree months. At what level of Ammonia do I need to be concerned for fish health? I have 7 koi 2" to 5", which appear pretty tolerant of water chemistry but they are more expensive than godfish so I don't want to kill them with high Ammonia levels.

The PH is low at 6.0 and I am having trouble raising it. Ammonia, nitrite, and nitrates were all zeroes until the recent Ammonia spike from 0.0 to 0.5. My plants started to seriously wilt recently as well but could be PH related. I was worried about nitrates being too low for the tomato and cauliflower plants. Today I added a 1/2 tsp of organic blood meal since I have five lemon cukes that I understand vacuums up a lot of nitrogen. Last week I dosed with iron and Maxicrop to no good affect.

On a side note some of the poop is being mineralized in the FT. My fresh koi poop is big, heavy sausages that the pump can't lift into the impeller so it breaks down on the bottom of the stock tank. I suspect that might be a source of some Ammonia but I am prepared to be wrong. I'll rearrange the FT pump away from the GB drain to suck broken down poop fragments into the GB and add soe composting worms.

I'm amending water blindly and hoping for good results but I feel like I'm chasing my tail. Any guidance is appreciated.


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You can calculate it out against your temps and pH...    and then compare that against the toxicity parameters listed for your particular species...

Get your pH into a readable range quickly...or you risk a total system crash. (If you are using the API test kit, you have absolutely no way of knowing whether your pH is at 6 or at 5.5...or 5...or 4.7...or any value below 6. Make sense? If the test kit only reads to 6 you could be either at 6 or anywhere below 6...

garden store - calcium hydroxide (hydrated lime).

Thank you Vlad & George. I'll jump on this tomorrow AM.

You're welcome.

Order some potassium hydroxide.  See Nate's video on PH adjusting.  If you want an easily managed system, add another grow bed.  One to one is good but two to one is better.

I may have thought of why I got the ammonia spike. Just before seeing the ammonia elevate I harvested my sweet peas so I pulled the plants from the GB. At the same time I pulled two corn stocks damaged by winds (they had deep roots). I suspect the system's ability to mitigate ammonia diminished with fewer plants processing some of it directly. To test the theory I'll need to transplant some garden center plants, flowers or veg, and hope they tolerate the tranpanting.

Yup, significantly disturbing the bio-filter has for many folks resulted in mini-spikes. They don't seem to last real long though. 

Good luck not picking up any unwanted "hitchhikers" from the store bought plants...(pathogens and/or pests)...

(You still really want to get you pH up into a readable range)...

Thanks Vlad. I've gotten the PH to 6.8. I hadn't thought about the "hitchhikers". Thanks for mentioning it. The ammonia levels seem stuck now at 1.0. My bacteria doesn't seem up to the task of processing seven koi though.

Meh...just quit feeding them for a week or two, they'll be fine...wait for the bloodmeal that you added to break down (it's mostly N), and you bacteria to pick back up. Fish produce a good amount of NH4 just by breathing.

How big is your bio-filter anyways..? 45 gallons of media? 45 gallons total volume? Or does it hold 45 gallons of water after being filled with media..? etc...

The GB holds 45 gallons of media and accepts 25-30% of the FT water. A complete fill-drain cycle is ~12 minutes and I turn the pump on for thirty minutes then thirty off so one complete tank change happens every two hours.

So that's like what...6 cubic feet of media? Seems like you should be ok with 7 little koi. The bloodmeal, the disturbances and the too low pH probably all contributed a little to the spikes. It's probably not a good idea to tax your bio-filter with additions of N that need to be broken down (unless you have large bio-filter(s) and capacity to spare). In the future if you feel you must add some N to save your plants saltpetre would be a better choice since the N is already in the nitrate form and does not need to be broken down. It will also give your system a bit of a boost in potassium (which is usually good)...

Just don't go adding ANYTHING without thinking through or knowing how that substances presence will play out in regards to bacteria, fish, plants and water chemistry.

Vlad: Thanks so much for the reassurance and the tip of saltpeter--I hadn'theard of that one before. Regards.

Sure thing txdurk .  Saltpetre is pretty much just unrefined potassium nitrate (KNO3)...unrefined in this case means that it still has about 25% or so calcium nitrate (CaNO3) in it (which is also great for plants). I've made my own from from all 'natural ingredients' (god that term sounds corny...I've not had any reason to use it in the GH system) but I'm sure you can easily just buy some. You might get flagged and probably spied on by some silly government agency or another if you go around buying pure KNO3, so saltpetre is a better bet...

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