Fishless Cycling Bafflement: Ammonia Stalled - Advice Welcome

I started a fishless cycle in my RO water (internally filtered) tank on 15th June, bumped with API Quick Start, Prevent Algae, Stress Zyme, Stress Coat (topped up weekly) and using ammonia to 2ppm (later shifted to 1ppm when I realised I'd misread the colour). No plants to date, but two large pieces of bogwood. Artificial sand substrate, so agitated weekly along with the water change.
Started off fine, ammonia from 1ppm to 0ppm in 24 hours, a week so later, the nitrites started to shift, 90% water change when they were over 5ppm for a few days. Had the temp up at 28-30 degrees C after the first week.

pH values between 7 and 7.4 most of the time. Sudden dip to 6.8  a week ago so I added 1/8 tsp of bicarb of soda (know of the downsides but there will be a pre-fish water change) to my 80 litre tank - 98 litre tank with 80 litres of water in, that is (full given the bogwood etc).

Problem: the other half of my household didn't like the filter and bubbling noise so it was turned down from about two weeks ago til a couple of days ago (against my preferences). (In the longer term it is going to be 25% or more planted so hopefully no long term bubble fights.)

This didn't affect things for a while but then my ammonia-eaters slowed down. From cycling 2ppm in 24 hours they went to taking two days or so to clear 1ppm, and after the last ammonia dose three days ago, it took twelve hours to go down to 0.5ppm ammonia and has been stuck there for the last three days (I'm checking every 12 hours).  Nitrites have been 0 for weeks but for the last few days I'm not sure if that's because there's little being produced.

Ph is now at 7.8 (KH and GH both between 60ppm and 90ppm). I'm aiming for a 7.0 or 7.2 final pH with temp. 24 degrees for my beginner fishlist.

I'd understand the stalling if my nitrite levels were elevated, but nitrites consistently 0 and nitrates 80ish (API master test kit).

The filter is now up and I've turned the temp down a shade (still over 27 degrees c) - do I just sit and wait for the ammonia eaters to get their stride back, or am I missing an essential action or a fundamental problem?

Thanks Sue (and for your reply on the alternative cycling topic) - very helpful.
I had thought the bubbles as well as filter water movement were needed to keep non-planted tanks sufficiently oxygenated? As I had small-particle substrate and no plants in yet, I've been extra worried about anaerobic build-up and wasn't sure how much surface agitation is essential.

Last night the pH was 8 but this morning 7.8 despite no changes from me.  This morning I  added 2 teaspoons (hopefully not too much too quickly) of Electro-right (which I got after the pH dip so I didn't have to use bicarb. again), so have this morning. (Need to double check that wasn't four actually - my notes are at home.)

This seems likely to mess the pH up again for a while. I had been hoping to avoid having to use pH adjusters over the longer term - we'll have to see.

I hadn't added the Electro-right earlier as I'd read that for soft/medium soft preference fish KG and GH between 70 and 100 was about right, so I hadn't thought to tweak it up.

I'll recheck the RO water but from early tests of tankwater at startup and for awhile thereafter nitrates were 5.0 ppm. 

(BTW I tested the substrate with a little RO water and that was pH 7 / 7.2, but my other half picked some aquarium rocks out at the store and I don't have the packaging still - they are black pebbles, and I haven't checked those.)

I'll update this thread if there's anything worth reporting (including getting to adding fish point, of course).

Thanks Sue. I may turn the bubbles down then.

On the water messing - I am a first timer and trying to get myself trained as well as the tank, so I was hoping to get a decent low-ish intervention equilibrium before disturbing it with plants and then fish.

Your hero ranking is well-deserved. Wondering whether there should be a superhero status award.

In the first post, he said he was using RO water  But I don't know if that's 100% RO or an RO/tapwater mixture.

If it is 100% RO, he will need electro-right or something similar to add minerals, and quite likely bicarb as well to get his KH high enough, but he won't need dechlorinator.
With 100% RO, he would also need a bacterial starter or donated media as RO won't have any filter bacteria in it. Though Quick Start and Stress Zyme are not among those reputed to work. Tetra Safe Start would be better; even if it doesn't work all the time, it does work more often that other brands.

Blame my slowness on the heat. I don't cope well with hot weather 

I do agree that using RO is not a good idea for a beginner. And yes, it would be better to cycle with whatever comes out of the tap, and then alter the chemistry with RO very slowly and carefully once the cycle has finished. If even then.
a_llusive says he is aiming for soft to med soft - that would suggest he has hard water and doesn't want to keep hard water fish.


Looking again at this thread now that the temp has finally dropped a bit and my brain is starting to work, it does look as though the cycling problems are due to using RO water. Assuming he has hard tapwater, the best thing for him to do would be drain the tank, fill it with tapwater adding only dechlorinator and complete the cycle. Once it is finished, then he could do small water changes with RO while adding ammonia every other day until the water reaches the pH and GH he is aiming for. Then maintain it at those levels by using a tap/RO mixture rather than pure RO with remineralisation salts. Adding RO slowly should not affect the bacteria too badly, and daily testing would show if they were coping with the drop in hardness or not.

Do you agree?