To Add Or Not To Add, And, If So, What?

Hi,

I have a very soft / soft water, PH ~6.4, 54-litre (60cm long) aquarium, with 6 x-ray tetras and 6 pygmy cories. Every now and again, I get an urge to add to the brood (eg a shoal of 6 ember tetras, to add some more colour and activity to the tank), only to convince myself that I'm risking getting near full stocking capacity and should instead set up a second aquarium if I want more fish. However, there genuinely isn't room for a second aquarium in our small abode. Any suggestions - is there an alternative that I could consider (eg a pair of or a single small fish or even an invertebrate) which would be compatible with the existing tankmates and water parameters and tank size, and which has less of a bioload than 6 ember tetras?

Thanks in advance for any thoughts/suggestions.

I'm going to disagree with Sue here. I don't think there would be any problem adding the Ember tetras or similar. I have four tanks in the 60 - 85 litre range which are stocked with shoals of tetra at 100 -120% of the CC's level. They've all been in for a good while with no problems whatever, all healthy and apparently happy. And I make far less water changes than most.

Tetras make low demands on a tank. They are pretty lightweight for their length. don't race around all day like danios and aren't greedy pigs like barbs. They are also happier in numbers, I have found that 20 - 30 tetras of 2 or 3 species together are far more confident than, for example, 10 of one species. They don't mind being crowded, in fact they seem to prefer it. In the wild they often live in close-packed shoals of thousands.

If you are still concerned, you could add a second small filter which would take you into the "oversized internal" region without making too strong a flow.

I've had a look a couple of times now at the miniature rasboras (and the ember tetras) but have been slightly concerned for their potential welfare .v. the two largest tetras. These two largest tetras have a tendency from time to time to chase the other four if they come close to their respective territories/'staging posts' in the tank (although have been fine with/ignored the cories in recent months but, in the first couple of months, looked on occasion to be contemplating the unmentionable).

On the other hand, I completely and utterly fell for the beauty and behaviour of some harlequin rasboras last week which were swimming beautifully in a big school up and down the upper region of the tank in the aquatic shop. This activity and occupancy level/height in the tank, if it remained when in a small shoal of 6, would complement the tank really well (as most of the time there is little activity with the cories 'chilled out' on leaves or on the substrate and the tetras at their various staging posts) BUT would push my stocking level with the one filter up to 100% (or 94% from recollection with two filters) - and that's not taking into account decor, substrate, and the fact that the tank isn't filled to the brim.

Ideally, if I were allowed to have the old/spare/quarantine tank as a permanent fixture, I could move the cories into that, with some embers or miniature rasboras, having the tetras and the harlequins together in the bigger tank. I've spent almost the entire day today trying to clear out, in the hope that the extra space I've created might be "rewarded" with the old/spare tank being allowed to become a permanent feature in the space created (I've even set it there in the hope that it might become 'contemplatable'), but I very much doubt that this will be the case.

How risky would it be adding the harlequin rasboras to the current tank? I currently do weekly water changes, and don't find this a chore at all given that the tank is smaller than the goldfish tank I used to have and so water changes are easier than those I'd been doing for many years, and the nitrates have never gone beyond 15. I'd be happy to increase these water changes to twice weekly (or more, if need be). However, I don't have any real plants (only silk ones), given that the tetras didn't/don't like the lighting on. In the event of a power failure, or the couple of times per year when I might be away for a week and so could only do one rather than two weekly water changes, would this be running a risk?

To continue on from Sue's point, in my opinion Espeis rasbora are more attractive than Harlequins. They are called Copper Harlequins at my local MA, and even in the store they are really vibrantly coloured. I was very close to buying them until I was introduced to the Neon Red Rainbowfish...

They were definitely Espeis in the tank at my MA. Hengelis are more translucent and with a smaller copper line around the black  area... hmmm....

Thanks, both.

My local MA has only ever had 'harlequin rasboras' or 'harlequins' (ie not been specific about type) on their labels - I've never seen a tank there labelled with any of the other types of harlequins (although I had looked out for espeis/lambchop/slender). I'll try and find out from them what these are that they had in last w/end.