Help! Sick aquarium fish

[Wigeon]

We have a 24l tank with beginner's fish (one platy, some danios and minnows). One platy already died a few weeks ago, and now the other platy is struggling to swim up the tank, keeps sinking to the bottom, and then falling over on his side.

I've googled the hell out of it, and it sounds like it might be swim bladder, or poor water quality - I've done a big water change (50%), the readings of ammonia and nitrite look like zero each (with the testing strips) and nitrate looks like it's under 20. We usually change about 5 litres of water every week. We also regularly put aquarium salt in when we do the water change.

We've also tried not feeding them for 2 days in case the problems is over-feeding, and putting a cooked pea in there a couple of days ago - which all the fish are completely ignoring.

What else can we try? The platy seems like he's getting worse not better.... DD was really upset when the first platy conked it and we had a little burial ceremony for him in the garden!

24l isn’t big enough for all those fish, it’s only barely big enough for a few Minnows.

Also, did you do a proper fishless cycle before adding the fish?

If you followed typical pet shop advice and set the tank up and put fish in a few days later they’ll be dying from ammonia poisoning.

Also, I only kept soft water fish that hate salt like terras and cories but I am fairly sure that none of the fish you listed particularly benefit from salt, asfaik none are brackish fish.

Frosted is completely correct. It annoys the shit out of me that 24 litre tanks are even sold. If possible, OP, could you stretch to 60l? There are often some cheap on FB marketplace or Gumtree.

I agree with the above poster.

Was your tank cycled properly? 50% water change, especially if you have washed your media in fresh water will have crashed your cycle too.

Salt is not needed for freshwater fish. Hints in the name really. Freshwater fish need fresh water and salt water or marine fish need salt water.

The peas need to be shelled too so maybe that's why they are ignoring it.

You do have way too much fish for a tank that small.

Do a 10-15% change every 2-3 days to dilute the salt and stop adding anymore in. Use something like seachem prime to condition the water and help stabilise the cycle.

Just posting quickly to say thanks for replies, and I’ll post again this evening when I’m back home and not at work.

Thanks again for your thoughts.

@frostedviolets, @AnduinsGirl and @cookiemonster5: there are 4 danios, 5 minnows and the sick platy in the tank. We followed the advice of Pets at Home re the number of fish for the size of the tank - they have a "fish points" system where they tell you the max number of points for the size of tank, and then each kind of fish has a number of points. So a 24l tank is 12 fish points, minnows are 1 point each, danios are 1 point, and platy are 2 points. So we have fish totalling 10 fish points total at the moment, which is slightly under what they recommend as the maximum.

So do you reckon Pets at Home are just trying to sell loads of fish / make lots of profit, and over-stock people's tanks? (Although these fish cost very little each, so the profit margins must be very small - although maybe they sell large volumes given they're popular beginner fish?). The staff member we spoke to there did seem to know her stuff - she said she had three tanks herself at home.

We've had the aquarium since June 2019, and we did do a proper fishless cycle, I think for at least 4 weeks or maybe 5 or 6, before adding in any fish, and even then we added them in gradually (2 platys on 13 July, then 4 danios on 21 July, then 5 minnows on 31 August, according to our Fish Logbook).

We have kept a record of all the ammonia, nitrite and nitrate readings since July (23 dates when we tested the water from July to now), and although there was an initial spike in ammonia to 3, we got it right down quite quickly, and since then it's been 0 or occasionally between 0 and 0.5. So I don't think it sounds like ammonia poisoning?

Nitrite has been 0 for ages; nitrate often seems to be 20-40.

Re the salt: that was actually what Pets at Home recommended when the first platy got sick! The packet also says "for freshwater fish: use when setting up a freshwater aquarium, changing water and treating fish disease". [https://www.apifishcare.com/product.php?id=628#.XkwtyZP7QQE it's this sort]].

So we thought we were doing something positive for the poor previous platy . Is this another case of a company trying to sell a product that's actually bad for freshwater fish?

Peas - I microwaved one til soft, and then shelled it. It's still there...

Any other thoughts with all this additional info? I did read that the test strips can be quite inaccurate, so wondering if the readings we apparently have aren't correct, we should get some kind of more accurate testing method?

Sorry, working link to the aquarium salt: here

At our local garden centre fish department they sell swim bladder stuff to kill the bacteria that causes this.
Our platy died of this 3 weeks ago and I had no idea there was stuff you could get to help this

They do this in pets at home for £5 too. Worth a try?

4 danios, 5 minnows and the sick platy in the tank. We followed the advice of Pets at Home
Overstocked.

IMO, they should be in a 60L minimum and I don’t personally feel a 25L is adequate for any fish, not even shrimp though many would disagree re shrimp.

I do sometimes see people recommend a Siamese fighting fish (Betta) for a 25L however, I did have a Betta once in a 25L and he wasn’t terribly active and I always felt a bit sorry for him, I got a 250 L and he used absolutely every bit of that tank and was very active swimming about exploring everywhere.

I guess what I am trying to say is the bigger the better, it’s really not fair to squash them into a tiny tank.

It’s not just the size of the actual fish to be considered anyway, it’s their personality as well.
Danios are typically very active fish so they require more space in order to behave naturally.

Smaller tanks are trickier to keep stable and healthy as well.

So do you reckon Pets at Home are just trying to sell loads of fish / make lots of profit, and over-stock people's tanks?
Yes, yes I do.

2 platys on 13 July
I don’t know the typical lifespan of this fish as I’ve never kept them but it’s possible they have died of old age maybe?

was actually what Pets at Home recommended when the first platy got sick! The packet also says "for freshwater fish
Aquarium Salt can IMO be beneficial in a quarantine tank for treating acute illness but it isn’t something I would add routinely unless it’s a Brackish (likes slightly salty water) fish species.
There are certain fish species, cories for example that can’t tolerate it at all.

Pets at home Unfortunatly have told you the wrong information. You need a much bigger tank or far less fish. I'd advise Esha 2000 if you can it's pretty good.

Also, forgot to mention, Danios, minnows and Platies are all social fish, they’d all do better of minimum 6, preferably 10. In a much larger tank

Never ever listen to pets at home. The rubbish most of their staff say is completely wrong. Research yourself. I've been in there buying plants and ended up with customer come up to me asking me questions after hearing me telling my kids about the fish because they do t believe what the staff are saying.

Add fish a week apart is too soon imo. You need a couple weeks to make sure the bioload is being managed by the tank and that no fish are sick or diseased if you don't have a quarantine tank.

Are you using a decholorinator when changing water?

@tessiegirl - ah, that’s good to know - although presumably you can’t treat the whole tank if only one of them appears to have swim bladder (possibly?). Do you put the sick one in a separate container somehow?

@cookiemonster5, yup, using dechlorinator in the fresh tap water every water change. Also, surely whether or not we stocked up the aquarium too fast seven months ago can’t be causing illness in one platy now, considering the ammonia levels have been zero or very close to zero for many months now?

Re doing our own research - I’m finding it really hard to find authoritative advice - multiple google searches turns up mostly fishkeeping internet forums, with all kinds of advice, or various pet shop / pet supplies website. I need some kind of NHS advice website, but for fish!

I get the point about a smaller tank cramping the normal behaviour of the fish, or not allowing us to keep sufficiently large numbers of them to be happy in good sized social groups, and obviously that’s not good for their overall stress levels, but would it actually cause one to be displaying the symptoms the platy is currently showing? That is, sinking to the bottom, generally staying on the bottom, tilting on one side.

We thought going to a major pet retailer and taking their advice before getting the fish was the responsible thing to do ...

@frostedviolets the internet reckons platy lifespan is 2-4 years. We’ve only had them 7 months but we don’t know how old they were when we bought them - but I guess on the younger side, given the likely turnover of stock at the fish shop?

Do you put the sick one in a separate container somehow?
You put the sick one in a separate tank, a ‘quarantine tank’.

Re doing our own research - I’m finding it really hard to find authoritative advice
Ah, like so much in life I suppose.
Everyone has a different view on everything, even those who are meant to be professionals.

but would it actually cause one to be displaying the symptoms the platy is currently showing? That is, sinking to the bottom, generally staying on the bottom, tilting on one side
The tilting I think is probably an actual medical issue; age, swim bladder, infection etc
Stress absolutely can and does cause fish to go a bit lethargic, staying on the bottom though.

the internet reckons platy lifespan is 2-4 years. We’ve only had them 7 months but we don’t know how old they were when we bought them
Hard to say but I wouldn’t be surprised if it was old age.