Hi,

I have an inherited Fluval Flex 37l with 3 zebra danios and quite a few platy's. Hasn't been maintained much, but fish all seemed healthy. I refreshed the setup about 10 days ago, some new substrate and couple fo new (artificial) plants. Add conditioner stuff etc that was used when tank was originally set up, left for a couple of days and re-added the fish with water from the original tank (that was in the bucket with them.)

They've all been fine, apart from one of the danio's that's alive, but has been staying at the bottom/back of the tank and only occasionally venturing up. I just noticed him today stuck in one of the small plants. I dislodged him, but he looks quite disorientated, and is sat mostly at a 45 degree angle, nose down.

Not sure what to do, doesn't look happy!

Did you use the existing filter and its media? If not, then the tank won't be cycled and you'll have ammonia and/or nitrite in the water which will make the fish sick - weaker ones more likely to show symptoms. If you haven't already, get a liquid-based test kit so you can test for ammonia and nitrite, and if either is showing (nitrite could take a few days to show), follow this guide to fish-in cycling. https://www.fishkeeping.co.uk/articles ... ammonia-nitrite-spike.htm

OK, thank you for the reply. I did replace the filter (foam part) but the carbon and media inside are the same.

I'll shoot to pet shop now and grab a test kit.

Firstly, is it worth taking him into a smaller bowl on his own? Just checking now and he's lodged into one of the plants again. Fear he might do himself more harm.

No, he's better off with a filter; though if you replaced the sponge that will have affected the cycle so do get the test kit, and as a precaution, start changing 50% of the water daily in the meantime.

Ok, I wasn’t sure and have got him in a net, still within the tank. The main reason is that some of the other fish kept going up to him and pecking at him, which would make home thrash a little and that’s when he was getting caught in the plants.

I didn’t get a chance to get to the shop, so have ordered liquid test kits from Amazon. Nitrate one comes tomorrow and ammonia one the day after.

It's nitrite you need at the moment, not nitrate.

Sorry, yes, that’s what’s coming today. Nitrite test kit. 👍

OK, got the nitrate test kit today. Tested the water and it's showing at about 1. So looking like it needs some water changes to bring it down.

I've replaced 5 litres today, although I'm not sure how I can change anymore at one time. I've got a 5 litre bottle that I'm adding the tap safe (Fluval brand bottle) to and letting that get to the same room temperature, then removed 5 litres from the tank and replaced with this.

Other than getting more buckets/bottles is there any other way that I should be doing this?

That doc mentions if nitrates are exceptionally high, change 50%, but I'm guessing that 1 wouldn;t be classed as exceptionally high?

1ppm nitrite is very high so change enough to get it below .5

Just tested again. I'd say it's looking closer to 0.25/0.5.

What's best now, do another change in the morning? I don't really have a way to change more than 5 litres at a time. Unless there's a suggestion on how best to change more?

Also, the tap safe additive I have, (Fluval bottle) doesn't really say how long it takes to work. Any idea how long it needs to be added to the new water, before I add that to the tank?

Sorry for all the questions, just don't want to get it wrong!