Nightmare!

[EmmaBemma]

Hello. Having a bad time just now and would really appreciate some help.

Went on holiday a couple of weeks ago. Left instructions with neighbour for feeding our two tiny goldfish. These can't have been clear enough, because on our return, one of the fish was lying on the bottom of the tank, clearly very ill, and the water was filthy, with lots of uneaten food and general murk, so I assume they'd been very over fed.

Filled another smaller tank with treated water and quickly transferred both fish and filter media. But two sponges were so horribly clogged, i decided to rinse well under tap because assumed there would be enough reserve bacteria in the unrinsed media. Emptied first tank and refilled with tap water, then treated this - I now realise I must have killed all bacteria in the gravel before putting the dechlorinator in.

Maybe you can tell where this is going. Transferred fish back. No improvement in ill fish and two days later he died. Tested water - ammonia 0.5 ppm. No nitrites. Think I must have killed most of the bacteria in trying to save the fish and now the tank is cycling.

Other fish now ill. Spends 80% of time lying almost immobile on floor of tank looking near death, but is eating and sporadically active. Am doing 40% water changes daily (80 litre tank) to keep ammonia as low as possible. Yesterday was nitrite spike at 0.25 ppm, ammonia 0 ppm, nitrate 10 ppm. Today ammonia is 0.25ppm and nitrite 0ppm. Nitrate still 10 ppm.

What is going on? How long will it take the tank to cycle and am I doing the right thing by changing the water so much, or prolonging the process and thus causing more pain for the fish? I don't know if he'll get better but I don't want to make him suffer any more than I have already.

[EauRouge]

Oh no, rinsing the sponges under the tap would have killed off all the good bacteria :( the chlorine in tap water is added to kill bacteria- good and bad. The gravel doesn't have that much good bacteria, the majority of it is in the filter. The unrinsed sponges probably don't have enough bacteria to sustain the fish but it will spread.

Yes, you are absolutely doing the right thing by doing lots of water changes. This is the only way to save the fish. It may take a few weeks of doing extra water changes.

Do you know anyone with a fish tank that can give you a bit of their filter sponge? Alternatively you could buy some ammolock or some bactinettes if your local aquatic store sells them. This can save the day if the filter has packed up or if the bacteria dies off for whatever reason.

How big is the tank?

[EmmaBemma]

hi eau, thank you for replying. yes, as i said, i knew it would kill the good bacteria but my reasoning (such as it was) was that there would be enough in the unrinsed sponges to repopulate them, as i'd remembered reading here that just one piece of old filter media is enough to seed a new filter, if you see what i mean. but obv i know now i was wrong. i was panicking really, just wanted to get the tank straight quickly so the fish could go back in and hopefully get better.

tank is 80 litres - i know not ideal for two goldfish long term but i was on top of the water quality before the holiday and they were quite happy in there.

Ammolock sounds good. but doesn't there need to be at least a little ammonia for the ammonia-eating bacteria to make nitrites for the nitrite-eating bacteria? it's all so confusing!

[EauRouge]

Oh right, I get you now. Yes, a bit of mature filter media can seed a new tank but it still takes a while for it to cycle.

Ammolock converts free ammonia (NH3) into less harmful ammonium (NH4+) which is still used by the filter bacteria. Don't ask me how the extra hydrogen atom gets there You'll still need to keep the nitrIte level down though because that is harmful too.

[EmmaBemma]

ok brilliant - I'll get that then. And presumably the water changes will keep the nitrite level down in the meantime. How will I know when the tank is cycled? Will ammonia and nitrite be O and nitrate be higher?

Thanks again for your help.

[EauRouge]

Yep, when ammonia and nitrIte are back at zero then it's all done. Hope your fishies are OK!