What's going on in my aquarium??

[GroggyLegs]

Hi all, I really hope someone can help because the aquarium shop is as clueless as I am. New fish owner.

We bought my son a micro aquarium (interpet 28L cube) in March and it was running really well - only 4 rummy nose tetra as we were stocking slowly.

Fast forward 4 weeks or so - We went away for 5 days, returned Thursday last week. FIL swears he fed them to my instructions (4 flakes, crushed up) on the Tuesday. I did a 20% water change before we went, water tested fine.

Came home to find them all nearly dead. Did it an emergency 25% water change & they recovered okay.
I realised I had fucked up with the filter which is a cassette supposed to be changed monthly, and did straight away & added safe start bacteria.

But ever since each night I'm finding the fish lying on the bottom or floating head down, apparently gasping, noses pale & washed out.
Testing (test tubes and droppers, not strip tests) shows raised nitrite.

When this happens I do a 20% change and next day they seem okay again, red noses, zipping about and happy to eat.

Aquarium place tested the water this morning and said it was perfect.

I'm feeding tiny amounts (4 flakes if tetramin every other day) to try & lower the nitrites but WTF have I done to these poor fish?

I have since added a sponge to the filter as I feel I must've removed a good chunk of the bacteria when I changed the cassette, even though that was as per the manufacturers instructions, but at a loss what else I can do.

Any one got any suggestions please?

Is it coming from their waste?

Have you fully cycled the tank before putting any fish in?

Your fish tank is too small for the amount of fish you have.

You have also removed all the good bacteria from the tank by changing the filter.

I'd be doing a 50% water change now, then 25% daily, to keep down the ammonia and nitrite that will be building up.

Ideally you need a bigger tank, and chemicals to test the water. Also read up on a "fish in cycle" which is what you are currently doing now you've changed the filter.

Manufacturers tell you to change sponges purely because it gives them more money. The only time you should be changing them is when they are disintegrating.

I've seen you've got a liquid test, which is the best thing to have.

You've basically stalled the water cycle, so it's like starting all over again. Daily testing and water changes when required, but you will need a bigger tank in the long run.

Tetras need at least 100l

Do you think FIL might be to blame?

If you're getting nitrites you've not completed the tank ammonia cycle, or you've killed all your bacteria and are starting a new cycle.

Get some Seachem Prime. Dechlorinates and adds bacteria at the same time. Also acts as an ammonia lock for about 48 hours so will protect the fish.

When you change the sponge next time (you don't need to do it monthly, you can just rinse it out) break some of the old one off and leave it in the filter to reseed the new one. Only wash/rinse the sponge/filter with tank water. Tap water will kill the bacteria because of the chlorine.

Thanks so much everyone - I wasn't expecting a response at all, so I really appreciate so many people taking the time to respond.

To clarify - there was no sponge in the filter (I know) it was literally a cassette which was two layers of floss with carbon inside - it's an 'easycare' system (this one is similar but has ceramic rings - mine didn't have anything except the floss cassette & the holder you slide it into) Where you supposedly pop out the cassette and replace it each month. The floss was very brown, slimy & gross, not a lot of filtering going on.

I have added a sponge today because it made zero sense that I was removing the bacteria (as well as the debris) with the filter.

Interestingly, the aquarium place had added their own to the one on display, but it didn't come as Thanks so much everyone - I wasn't expecting a response at all, so I really appreciate so many people taking the time to respond.

To clarify - there was no sponge in the filter (I know) it was literally a cassette which was two layers of floss with carbon inside - it's an easy are system (this similar one has ceramic rings - mine didn't have anything but the floss cassette) Where you supposedly pop out the cassette and replace it each month. The floss was very brown, slimy & gross, not a lot of filtering going on.

I have added a sponge today because it made zero sense that I was removing the bacteria (as well as the debris) with the filter.

Interestingly, the aquarium place had added their own to the one on display, but it didn't come as standard in the tank.

@GCITC I think you're right & stalling the water cycle is probably exactly what I've done & will cary on with the regular changes in the hope it stabilises.

@Haggisfish3 - I use a Syphon but I think I'm a bit crap at it.

@Undecicive - yes, the tank was cycled and running well pre-holiday. I felt I was getting the hang of it (cries).

@AndSoFinally - I use Tetra Aqua safe every water change and have been adding safe start bacteria. Is the prime product better? I don't have problems with ammonia per se, but I assume locking ammonia would have the knock on to stopping nitrite production?

@AGritThatThrobs - who knows what he got up to, but he swears he followed my instructions!

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@AGritThatThrobs

Omg, sorry - I'm not sure how I managed to mess that up so royally 😫

I remember once we cleaned the tank, 25pc water change and all the fish started looking ropey. Tested water and it had nitrites so we did another water change. Then they all died. It was horrible to watch. Turns out the tap water had nitrites in that particular day after loads of rain. Water company say its not possible and never happened, but we tested the tap with two kits. Sure that's not your issue, just one to be aware of!

Prime is a really good product

Do you know anyone with a cycled tank who could donate you some media? If you were local to me I'd give you some and it would really help to get your cycle back on track.

You can buy ready cycled sponge filters from Tropco (they also do a pouch of Bacterial Goop which is amazing stuff) but they are expensive.

@GroggyLegs I really like Prime and the other seachem products. I imagine they're all much of a muchness. Does the tetra one have an ammo-lock element? This locks the ammonia in a harmless state for 48 hours which gives the bacteria a chance to build up. If it doesn't, I would try Prime. You'll only need about 1 or 2ml for a 28l tank. I would advise dosing for the whole 28l each time, rather than just for the amount of water you change. You can also use double the amount for a short time while the bacteria build up which gives you a bit of wriggle room

Prime counteracts the effects of ammonia and nitrite on your fish, giving them a better chance of surviving during the stall.

@PoopySalata - that's so generous of you, thank you. I will ask at the shop if they can help.

@AndSoFinally - I read up on the prime product & was amazed how little is needed in the dosing chart. Thank you for your guidance, it's arriving tomorrow.
Do you think it will be okay to start using it in a tank which has been dosed with the tetra product? I assume they do similar things but no, there's no mention of ammonia locking properties.

@Morechocmorechoc - yes, it's horrible seeing them in distress, sorry that happened. Did you start again or give up on fish?! I'll bear your experience in mind!

Our tap water has around 30 to 40ppm of nitrates. When we started our tank 4 years ago we had this problem as couldn't get the levels down. It might be worth considering using reverse osmosis water (although you have to add some salts and which most fish shops sell fairly cheaply) ever other water change to keep levels consistent. We've also found one of the cheap OL bottled spring water has very low nitrates so use that. Be careful though as some bottled water as chloride added which would kill the filter bacteria and there is a big range of nitrate levels across different brands.

We started again and no more issues since thank goodness.

@GroggyLegs yes, it's fine. Do a 20% water change and add enough for the 28l to the fresh water before adding it in.

I use houseplants to control the nitrates in my tanks

I think your problems probably began with overfeeding, albeit it accidental. You have then compounded the issue by replacing, rather than a light clean of your filter media. Like others have said, you need to in essence start afresh. I agree with others that your tank is too small for your tetra. You would probably do well swapping them do a Betta IMHO. Another consideration is planting, if you only have artificial plants you are missing a part of your tanks eco system in my opinion. Unfortunately fish keeping is one of those hobbies that takes a lot of trial and error to get your tank working well.