Advice on puting an internal filter into a small cycling tank

Those of you who have been reading my few posts will know that I went in to a petshop and was sold 3 small orandas (1") and 3 white clouds and told that they would be fine in a 20L tank.

And then doing things in the wrong order I started reading about keeping fish.

We are doing regular changes - and with the exception of an occasional fish gulping at the surface they seem healthy and active.

Today I found a fish shop that seems to know what it's at - and it's close enough to get to it from where I work - so I now have (among other things) an internal filter to add to the tank.

(For those of you whos brains are screaming 'too small, too small' at this stage; I know, I'm getting a larger tank - it just takes a while to work out where and how - today's visit to the shop also allowed me to actually see some tanks and get a better idea of just how big etc they are.)

My intention is to use the small tank as an emergency etc tank afterwards so I'm happy to equip it, even though I'm getting a proper tank as soon as I've worked it out.

So how do I set up the filter ?

- Immerse it in the tank and leave it for a while before plugging it in ?
or do I use it in a bucket or similar for a while first to rinse it etc. before putting it in the tank. I forgot to ask the chap in the fish shop - I had so many things to get sorted out in my head.

There is some fish poo in the tank, not a lot, but there is some that floats up when I do my frequent small water changes; 1+L x 3 times a day

Once I have it in placed in the tank and running do I avoid disturbing the fish poo on the bottom of the tank or do I intentionally disturb the bottom a bit to get the poo into the water and get it into the filter more quickly. Or will the flow from the filter do this for me anyway.

I did ask about a small airpump and airstone and I was told that for coldwater tanks in typical Irish houses the action of the filter moving the water is more than sufficient to keep the oxygen levels up - anybody want to give me a second opinion on this. It's not too warm here 60-70F in the summer and 30-40F in the winter with houses typically heated to 60F or so.

Thanks, John.

And a further thought occurs to me :

If I should run the filter in a bucket or similar first to rinse it then I presume I should add a bit of water treatment to the water first to avoid chlorinating the filters which might slow the initial take up of ammonia and nitrite consuming bacteria in the unit.

So I added my filter - it's the smallest I could get - suitable for up to 30 L - It's a Hydor.

I set the control to mid-way and stuck it to the side of the tank and plugged it in.

Woah - there was a serious current in my tank - that's not right.

So I took it out again - set the setting to min and put it back in on the side of the tank - still a pretty serious current.

So I did a rethink and stuck it to the back of the tank with the flow going forward and I moved the Eloida so the flow streamed into it in an attempt to break up the flow a bit.

But there is still a fair bit of water movement - the fish are fairly active and I'm not entirely sure they're happy about things. But they tend to get that way when I move things around so it's not clear how much is due to the change and how much is the current.

There are places in the tank which appear to have fairly quiet water, but the orandas seem to be swimming into the current a bit and occasionally one or aonther seems to be being pushed along a bit.

I'm wondering if they might get exhausted having to be more active than before - and it just seems to me that there is too much movement in the tank for them.

Any thoughts ?

I'm going to pop this up as a new question as it might get burried here.

John.