Fishless Cycling Problem

Those Hikari micro pellets are absolutely tiny, though - I'd say at least 8. Tomorrow, I'll measure out how much I give my 11 fish and then let you know.

Update:

I've taken a pic of my fishes' breakfast - broken pieces of Tetramin flakes plus Hikari micro pellets - to give you an idea of amount. NB. this feeds 11 fish, so you'd be aiming for 1/3 of this amount. I give them the same amount twice a day (although substituting the Hikari micro pellets with Hikari micro wafers in the evening). About twice a week, they get 2 chopped peas between them all as well.

If you find that fish food remains on the water surface several minutes after feeding, then best to net this out. You may find fungused micro pellets on the bottom of the tank during syphoning - this may indicate over-feeding although I tend to find that pellets inevitably fall before the fish notice them or behind their backs while they're feeding on other pieces.

I'd err on the side of under-feeding while undertaking the fish-in cycle - although hopefully my and Littlefish's mature media will help your filter be cycled very soon.

The best place to place mature media is at the end of the filter that water is drawn through i.e. if the filter pulls in water from the bottom and pushes out the top place it in the bottom.  That way the mature media is pulled through the rest of the media.

Ah ok, will move it from bottom to on top of green sponge and under white one.

Mature media as close to the inflow of the water as possible, so it sounds as if you've put it in the best place for your filter.
As for adding more fish, I'm really not sure. The more experienced keepers would give the best advice.
The amount of media I sent was half the media that I had in one of my temperate tanks, so would have been used to dealing with the waste from around twice as many fish as you have in your tank.
Plus the other mature media, you probably have the bacterial capacity to increase you numbers.
I'm not known for my patience when it comes to acquiring more fish, and I don't want to encourage any bad habits in others. 

My thinking was due to the mature media I didn't want to waste it as having only a few fish but makes sense not to rush things. My plan was to get 2 and then another 2 harlequins over the timescale you suggest and then move on to other fish. Main question would be which ones next. In the frame are Panda Corys, Marble Hatchetfish and Neon Tetras. Would you add them in this order?

I have silver hatchet fish in my South American tank. I performed a fishless cycle on the planted tank and added the hatchets, penguin tetra and glass blood fin tetra all at the same time. Also, as I'd used mature media from several tanks, it only took a couple of weeks to cycle, so not what you could call a mature tank by any stretch of the imagination. All inhabitants of that tank have done well.
I have panda cory in my betta tank. That tank was slightly more mature, but had only been running for a few months before I decided to get some companions for the betta. I lost one panda a while back, but apart from that they have been fine in that planted tank too.
I don't have any experience of neons, but the hatchets and pandas I've got seem to be quite hardy, so that agrees with what Sue is saying about order of additions. 

You can add more fish when the readings for both ammonia and nitrite have been zero for a week.

But not many more fish. You will have only enough bacteria for 4 harlequins, so in theory you can add 1.3333 more fish the same size as the harlequins

@Sue 0.3333 That's sound worryingly like a fish finger

Yep looking good @barneyadi
From your readings I calculate your Ammonia and Nitrate should have ended up as about 1ppm Nitrate so I guess you had a little bit of Nitrate in the water already... but the bacteria must be starting to develop
Good news on a tank cycle, I like that!

Help!!!

Checked readings now, and they are as follows

Ammonia 1.28
Nitrite 0.05
Nitrate 12.64

I know ammonia is high, should I use some Seachem Prime to lower it? Nitrates have jumped, is this good news? My thinking is ammonia is being converted to Nitrates which means tank is cycling but just want to make sure.

Ok here is the problem. I used Tetra Safe Start at beginning of cycle and according to them you shouldn't water change for 14 days as would affect the TSS. Wouldn't just adding Prime help reduce the ammonia? This is a reply from Tetra to a forum member on another site, hence my reason for asking.

You can test the water any time, but really, you should probably wait at
least 48 hours. We expect TSS to start slowly seeding the tank, and
making a difference in about that time. You have to have some ammonia
occur in the tank to provide the cycle needed, so it will usually create
levels or reduce levels to around 1.0-1.5 ppm, and they should stay
there for a week to 14 days, and then come down. Sorry, these levels
would be for both ammonia and nitrite. These are considered stress, but
not toxic, levels, and should not cause any long term damage to the
fish.

We recommend waiting two weeks before a water change. Of course, if for
some reason, the levels go up to a high level again, we would recommend
a change at that point, and another dose. Usually, the hobbyist has
done something wrong the first time, in such cases.