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I need some advice from the experienced.  I've been fishless cycling for 2 weeks, and I'm just confused with what's going on with my numbers.  The system is 5 growbeds made from food grade ibc totes filled 12" deep with granite gravel.  I tested the gravel with vinegar, no bubbles.  The fish tank is a whole ibc tote with the drain line set up at the 250 gallon mark.  The sump is a rubbermaid stock tank from tractor supply, 150 gallons.  The system is chist/pift.

The house water supply has a ph of 8.4, and I used muriatic acid to lower it. I haven't been scientific about it, I just added a little, waited 24 hrs then tested, and repeated until I got it down to 7.2. I let it go for a few days testing the ph and it was stable, so I added amonia up to 8 ppm, a bag of seaweed extract, and Mycorrihizae Bacteria Starter.

Here's the numbers over the next few days after adding all that and adding nothing else:


7.6 8 0 0

7.6 8 .25 0

7.2 8 5 20

6.6 4 5 80

6.2 2 7 130

6.0 .25 5 80

It was at this point that evaporation became a problem and I started adding water. Since the system ph was so low at this point I decided to add the water without treating it for the ph, just bubbling it to get the chlorine out. This is what it looked like then:

Added 8 gallons of water

6.8 0 2 10 Added ammonia up to 2ppm after this test (March 19)

Added 8 gallons of water

7.6 2 .05 5

6.4 .25 0 0 Added ammonia up to 3ppm (March 21)

At this point I started testing morning and evening, all above tests were evening.

6.6 .5 0 0

Added 8 gallons of water

6.0 3 0 0 E

6.8 2 0 0 M

Added 8 gallons of water

7.8 1 0 0 E

So to start with, it appears from todays tests that adding 8 gallons of 8.4 to 400 gallons reading 6.8 brought it up to 7.8. That seems like a much bigger than expected swing. Also I haven't added any acid for 2 weeks but it's continuing to drop except when I add the water and that seems to swing it way more than I expect.

Second, my ammonia is dropping but I'm not seeing any nitrites or nitrates. I do have a lovely crop of algae and have planted the grow beds, mostly by putting seeds directly into the gravel. I have just this evening blacked out the fish tank and yesterday I dropped a couple of plecos in there. Is it possible that the bacteria is converting the ammonia but the algae/plants are eating it as fast as it becomes available?

I thought I'd be adding fish soon but now I'm not too sure. Any advice?

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Replies to This Discussion

You tap water probably has had an effect on your pH but it is also likely that the algae could be having an effect on pH as well.  Algae can cause pH to rise through the day and drop through the night.

Algae and plants can also use up the nitrates as soon as they are available but algae is also able to use up ammonia directly and rob it from the bio-filter.

Now that you have blacked out the tank keep testing for a while to see what happens as the algae dies off.  Make sure you have some extra aeration cause a major algae crash can use up all the dissolved oxygen if the water is too still and I wouldn't want your pleco's to suffocate.

Once the algae has died off and your water tests show both ammonia and nitrite are 0 you should be able to add some fish though I would say start cautiously (keep testing and base your feeding on the tests, as in if ammonia and nitrite come up then you have to restrict or stop feeding till they come back down) since 2 weeks isn't long enough to be fully cycled but I wouldn't add any more ammonia now that you have added fish to the system.


  I totally agree with TC, the algae is feeding on the available nitrites and nitrates leaving virtually nothing for the grow beds.  I believe that after you blacked out the tanks and cut off the light the algae will start to die off and the nitrates will increase.  As TC stated be sure to aerate well or your Plecos will sufficate.  Please don't believe that a 10 gallon air pump will be enough to do the job, it will take 20 of these to do the job so size accordingly.  Be well.

White Bear

Thanks for the quick answers.  I do have 4 air stones bubbling away in there run by 2 60 gallon pumps.  If necessary I've got an air pump rated for 2000-5000 gallon systems, but at 50 watts I'd rather not run it.

I'll just keep watching it for now.  I'm glad to know the algae could be causing the ph swings, that was really messing with my head.


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