Backyard Aquaponics
A place to discuss aquaponics

Well, it looks like you are past the ph crisis. I've often found some systems sit at .25 ammonia rather than dropping all the way to zero.

If
1) ammonia has been sitting at .25 for days and
2) nitrite is zero and
3) water is clear and
4) fish are hungry,
I would say it is pretty safe to increase feed.

I've seen this too, like when collecting water samples from a heavily stocked/fed fish tank. Usually if I were to then collect a sample of water coming out of a grow bed, I would find that the ammonia in that water was 0 or at least undetectable by our tests.

Keep an eye on the pH from now on.

My ph is still sitting on 6.4...I think (it is darker than yellow but not any colour on the chart). I can't seem to get the ammonia level below .25. It has been sitting on that level for a long time now. I think I will start to feed them a full cup again and see what happens to my levels. Thanks for everyone's help....disaster averted. I will definitely be checking the ph regularly from now on. I have heard that some systems run on around 6 all the time so I was thinking that it was okay. I have planted heaps of seeds and can't wait for them to emerge.

I bet 6 is probably ok as long as it takes a few months to drift down that far, allowing time for low-ph bacterial flora to take over from the higher ph stuff. On the other hand, those bacteria might be rare enough or it might take long enough for your bacteria to adapt/evolve that it might take many months for your system to adapt without a crash.

I wonder what is the lowest ph that the bacteria our systems require can handle? Are there extremophiles that would do the job? (not that there are any fish or plants that could handle it)

Nitrofying bacteria seem to work in the soil down to about pH 4.5 or so so it seems there are strains around that will do the job as long as you avoid a crash and allow enough time for the right strains to build up.
John

Also seems to work in Biofilters
see the last sentence particularly
Title: High nitrification rate at low pH in a fluidized bed reactor with chalk as the biofilm carrier.
Personal Authors: Tarre, S., Beliavski, M., Denekamp, N., Gieseke, A., Beer, D. de, Green, M.


A typical steady state bulk pH of about 5 was established in a nitrifying fluidized bed with chalk as the only buffer agent. In spite of the low pH, high rate nitrification was observed with the nitrification kinetic parameters in the chalk reactor similar to those of biological reactors operating at pH>7. Various methods were used to determine the reasons for high rate nitrification at such low pH including (i) determination of bacterial species, (ii) microsensor measurements in the biofilm, and (iii) comparison of nitrification performance at low pH with a non-chalk fluidized bed reactor. Fluorescence in situ hybridization (FISH) using existing 16S rRNA-targeted oligonucleotide probes showed common nitrifying bacteria in the low pH chalk reactor. The prevalent nitrifying bacteria were identified in the Nitrosomonas oligotropha, Nitrosomonas europeae/eutropha, Nitrosospira and Nitrospira related groups, all well known nitrifiers. Microelectrode measurements showed that the pH in the biofilm was low and similar to that of the bulk pH. Finally, reactor performance using a non-chalk biofilm carrier (sintered glass) with the same bacterial inoculum also showed high rate nitrification below pH 5. The results suggest that inhibition of nitrification at low pH is highly overestimated.

While I adjust my pH toward 6.4-6.8.... whenever I notice it.... my pH is often around 6.0 (possibly beyond)

Others like F&F and even (from memory) some of Joels systems... run around the same level...

Note: these are mature systems....

I think it must be the maturity of the system. My ammonia levels don't want to drop down past .25. I fed the fish a full cup today and yesterday. This morning test results were not influenced by the increased feed.

Remember that there are two types of ammonia.
The test kits measure (tan) total ammonia, being the combination of both ammonia readings.
Hope that makes sense to others.

I have started to feed the fish a full cup again. Everything is looking good. Water results
ph 6.4
am .25
nitrite 0
nitrate 10
I was surprised that my level of nitrate was not higher. I have cleaned out a lot of the beds and planted seeds. I would have thought that the level would have been higher. We have had a bit of rain in the last few days that would have diluted my water a little bit. I have worked out that my level of ammonia has been sitting on .25 since the middle of June. I don't know why it wont come down

I remember early on with my system that the ammonia hovered above 0 though it looked lower than .25 to me. I realized that I was testing water from a fish tank. When I tested water that came out of a grow bed, it would usually test as 0.

Now that my system has lots of flow and filtration from many angles and has over a year of operation, the ammonia tests as 0 unless something is wrong. I've got about twice as much water and filtration as I need for the amount of fish in my system now though.

Depending on your system, it might just need more maturity to get rid of the minimal ammonia reading.

that' is a relief to know that it is normal to get a trace amount. It all started to increase when I tried to increase my feeding rates. I am thinking of increasing my levels soon... I guess I will just do it slowly and see what happens. I am still waiting for my seeds to germinate. The rest of the plants look really healthy.

You might also want to make sure you have buffering material in the system to help keep the pH from dropping any lower than it currently is.

I have got shell grit in the sump tank and under the grow bed inlet pipes. Hopefully that will be enough. I tested my ph today and it had dropped slightly to 6.4. I have added some ecorose.

I have made a few additions of ecorose over the last week. Probably 5tablespoons in total. My Ph does not seem to match any colour on the chart...I think it is around 6.4??? Unfortunatly I have run out of the test bottles for ammonia. does anyone know where I could purchase new ones? I don't want to buy a complete new kit.

I am still toying with the idea of replacing the pump in the main fish tank. the current pump is a second hand one and I don;t really know how much water it pumps per hour. I am thiniing of getting a ebara optima or a aquapro one. What does everyone think?? Are they the best pumps for the job?

I still don't think my water is that clear. It is impossible to see in at all. There seems to be bits of 'dirt' floating in the tank - Not a lot but some. Hopefully a new pump will do the trick. The fish seem happy and feeding. I think I will harvest one this weekend and see what it looks like.