HELP my fish keep dying!!

  • #1

I recently posted to say that my heater stopped working and that killed off my fish, but now I am thinking there is something seriously wrong with my tank! I have been running my tank on almost empty for nearly 2 months now, and all I had in it was 1 BN pleco, some shrimp and some assassin snail.

I am a teacher and I am now on summer holidays so this week I have set about sorting it out. I bought new substrate (caribsea super natural moon sand) and replaced the old stuff. I put the remaining fauna in my hospital tank, along with the fully cycled filter and set about scrubbing and cleaning all of my rocks/wood/plants with a new toothbrush so they looked nice. I left it for a day to settle and then added my existing fauna back into the tank. Checked my levels and all seemed fine, so I went and got 6 albino corys and an apple snail to introduce to the tank. Woke up this morning and the corys are all dead (apple snail seems fine). My existing fauna all are fine too.

These are my current levels, which look a bit weird to me:

Ammonia: 0ppm
Nitrite: 0ppm
Nitrate: 5ppm
I bought a new heater but for some reason my temperature is 95 farenheit which is much higher than I have the heater set to. Could this be the problem? I have turned it right down to see if I can get the temperature to drop a bit.

Is my tank going through a minI cycle? What on Earth is going on?

Please help as I am a bit lost and feel terribly guilty about the corys dying!

Any advice would be gratefully received!!

  • #2
HI Clare,

I'm sorry about your cories. Can you return them to the store for a refund?

Your water parameters look good. It could be the temperature for sure. How did you acclimate the cories?

Is the snail moving about in the water or is it above the water line? Snails will often leave the water when there's something wrong.

Since the heater seems to not be working, I'd remove it until the temperature is back in normal range again. You can facilitate cooling by changing some of the water and making sure there is good aeration. Add new water that is just slightly cooler than the tank temp now - about a degree difference - so you don't shock your remaining fish.

I'd start there and watch the other fish carefully. Good luck.
  • Thread Starter
  • #3
Thank you for your speedy reply!

I acclimated them like I usually do, very gradually over an hour to an hour and a half, adding in a little of my tank water after about half an hour and gradually adding a little more over the next hour until finally opening the bag and allowing the corys to leave the bag when they were ready. I have always done it like this and never seemed to have a problem before. The apple snail is wandering about all over the place. Looks happy to me!
I have replaced my heater with a spare and I am going to do a water change like you suggested.

I must say, I feel very nervous about buying any more fish now. I really don't want them to die! Once the temperature situation is sorted, when do you think I would be safe to put more fish in? And should I start off with a hardier species like it is a new tank again? Sorry for all of the questions, I have had the tank for about 2 years now but this has sort of made me feel like I am back at square one again!


  • #4
95F might be the ambient temperature and not a heater problem? I say this because yesterday was a very warm day in London, UK and my temperature shot up to 85F! I was shocked! It's really the highest temp my platys should eb subjected to. I now removed the lamp to decrease the temp. Luckily it is not that hot very often in London! But bear in mind your water will get as hot as the ambient air temp and you might have to buy a cooler instead of a heater! 95F is too hot for corys, probably why they died.
Also bear in mind you should not clean the plants etc in tap water but use old tank water. Otherwise this will cause another minI cycling of the tank. Not sure if you kept anything else in your tank, but replacing the substrate woud have removed all your good bacteria, so you will have to go through the cycle again. This would not have affected your corys that quick though. It would have been the temp
  • Thread Starter
  • #5

Yes I did use old tank water to clean them and although I did change the substrate I left my filter media well alone! Am I still to expect a minI cycle even with the old filter media being in the tank?

I am in Norwich UK and it is very warm here, 24 Celsius today (lush!), but my tank is in a very shady, cool corner of my room, against the old brickwork of my house, so hopefully it will remain cooler! I am very annoyed as that was a brand new heater that was in there so I am going to take it back. My other heater seems to be working well though as the temperature has gone from 35 Celsius to 32 in the last few hours.
I am fully thinking that it was the temperature (again) that killed my fish. I am gutted but hopeful that the next lot of fish I get will not die!

Thanks for your help!
  • #6
It needs to be around 25c! I'm not an expert but it seems far too high for me! Not sure what to do about it though sorry!
  • Thread Starter
  • #7
Yes it is way too high but I need to gradually reduce the temp otherwise I will kill the remaining animals in there! What a nightmare! Fingers crossed it will be down to the correct temp by this evening!

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