54-litre, Soft Water Tank Developments

I thought I'd create a new thread on developments in my tank - it might also be useful (especially for those with similar-sized tanks and water parameters - I have very soft water) on the various issues/considerations involved when choosing new species.

I used to keep goldfish (and still have a very soft spot for these), then took up tropical fishkeeping almost 5 years ago. Initially, I got a shoal of 6 x-ray tetras https://www.thinkfish.co.uk/fish/x-ray-tetra.html, of which I still have 3. Just over a couple of months later, 6 pygmy cories https://www.thinkfish.co.uk/fish/pygmy-cory.html joined the tank inhabitants - these were adorable but sadly didn't do well and succumbed one after the other between months 6-9 of their short lives, despite monitoring and keeping water quality at optimum levels and being very diligent about water and other aspects of fish welfare (as per https://www.thinkfish.co.uk/article/golden-rules-of-tropical-fish-care. About 5 months after getting the pygmy cories, 6 harlequin rasboras https://www.thinkfish.co.uk/fish/harlequin-rasbora.html were added, of which I still have 4.

Two nerite snails now also inhabit the tank - added in 2017 (tiger orange) and 2018 (red waigiensis).

Last year, as there had been a few fatalities among the x-ray tetras, and I had sufficient stocking capacity for more fish, after some deliberation https://forums.thinkfish.co.uk/general-fishkeeping-advice/restocking-54-litre-tank-now-that-numbers-are-depleting/10/, I opted for some neon green rasboras / microdevario kubotai, which would occupy the mid-upper levels of the tank along with the harlequins. Aware that the dimunitive pygmy cories hadn't fared well, and that advice is increasingly for larger shoal sizes in particular among such small species, I got 8 of these in the hope that they would do better; in a nutshell, they didn't do particularly well despite replenishing the shoal with a further 4 - I now only have 2 left.

I had toyed later last year, and intermittently again this year, about whether to add a bottom-dweller but this hasn't happened and I'm now putting that on hold. Some of these deliberations are included in the link above. I had also thought about a dwarf cichlid but, assuming that the x-ray tetras would succumb next (all 3 have visible health problems although are perfectly fine appetite/temperament-wise) and thus that the tank could potentially evolve into an Asian set-up, and a little concerned that a bottom-dwelling fish may not be the wisest given that at least one of the two nerite snails has a habit of spending considerable time on his back and I'm not always around to help rescue him, I abandoned that plan. I was still keen, though, for a/several fish that might inhabit the lower half of the tank and perhaps avail of any food that my fussy/spoiled gang ignored or spat out regardless of attempts at under-feeding them to make them appreciate such foods more. Although cherry barbs would be ok in a 60x30cm footprint of tank, I felt that they seem to get quite large - and I find their eyes aren't particularly visible, and eye contact with each fish is a feature I appreciate. Cardinal tetras seemed to fit the bill, are considered more robust than neon tetras, and Mr FCMF has always been keen on these but this choice didn't quite fit the Asian theme I had been veering towards.

In the past ten days, though, having lost a couple more neon green rasboras, one a total surprise (and there was a sudden harlequin fatality earlier this year too), I realised that the direction of my tank (Asian .v. S.American) wasn't actually as clear-cut as I had been expecting. The international mix has always fared well too - in fact, the dynamics has been such that the two older species or more recently the two more active species tend to pair up more than the same-cultural species do, despite being a cross-cultural mix in each case. I had thought about letting the tank continue as it was and starting with new fish altogether at some stage in the future, rather than replenishing it. However, ultimately at the end of the week, as a possible antidote to the sad fatalities over the previous week, I purchased a small shoal of 6 cardinal tetras, currently in quarantine. I'm hoping that this will complement my other fish nicely and that the good international relations will continue, with each species having its own merits - x-rays' colourful finnage and distinct eyes, harlequins' body patterning and distinct eyes, neon greens rasboras' cuteness due to their small size and higher activity levels, cardinals' colourful bodies and willingness to eat food from the tank substrate.

My immediate priority is to get the cardinals through quarantine and eventually moved into the main tank, ideally without problems - it's a bit nerve-wracking, after the neon green rasboras and several fatal accident deaths among them.

Any thoughts or suggestions on how my tank might evolve in the future, though, would be most welcome. Increasing the size of the shoal of cardinals is one possibility. Although tempted by dwarf versions of these https://www.thinkfish.co.uk/fish/golden-pencilfish.html, another thought is to add something entirely different to a shoal of fish - e.g. gourami (eg https://www.thinkfish.co.uk/fish/honey-gourami.html or https://www.thinkfish.co.uk/fish/sparkling-gourami.html), once the faster-paced species have dwindled. I am purposefully avoiding shrimp and any fish that would be likely to tuck into a dying/dead fish as these give me the heebie-jeebies - thankfully, my previous and current inhabitants have been very 'respectful' in that regard.

Would Otocinclus be a useful addition to your tank. Good algae eaters and quite comical to watch their antics.

Thanks, all. 

I think boosting the number of cardinal tetras is almost certain but I don't plan to boost the ageing species (prefer to have fond memories of each of them and their unique personalities and interactions than have this diluted by new ones of the same species) or the neon green rasboras (which didn't fare well). However, I wouldn't be averse to espei or hengeli rasbora in the future due to their lovely patterning but just a little bit different from my current harlequins - it's likely that the harlequins may not be around by that stage, though.

Does anyone who has kept sparkling gourami in a small tank have problems with them fighting or perturbing their tankmates with their croaking sound?

Otocinclus might be an option if I revert to live plant-keeping in the future and thus have more algae, but this is "off the cards" for the time being. I'm also almost certain I've seen some in a LFS sucking the algae off a dying/dead fish which gives me the heebie-jeebies.

The ember tetra is what I considered previously - but then fell instead for the harlequin rasbora. I might re-open my mind to that possibility again, though, despite my uneasiness on the basis of adverse experiences with dimunitive species.

Thanks. CPDs are indeed lovely but sadly require harder water than my 1.86 dH and 33.16 ppm. Even some limestone rock in the tank, there to prevent a PH crash, doesn't increase the hardness much at all.

Hmmm, I do like the sounds of their characters - but the inability to identify everyone on a 'roll call' would have me dismantling the tank on at least a daily basis...

I ran at 95% for a short while and remember it being hard work keeping on top of maintenance though it doesn't sound like this will be a significant problem for you. I guess it's a question of how long can you wait/what is the status of your current non-cardinals.