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Cleaning out old fish tank

4 replies

grendel · 06/04/2014 15:59

Our two goldfish suddenly died some time ago. Since then I've kept the pump going to stop the water going manky but have just left it to its own devices, planning to sort it out every weekend but never getting round to it.
Now 6 months later (cough) we really want to get some new fish but I'm not sure what to do about the tank. If they weren't fish I'd be inclined the scrub the whole thing out with bleach to ensure that none of whatever lurgi killed the goldfish remains. But since the tank will hold fish, any recommendations on how I should clean the whole thing out safely (including gravel, plants etc) so that it can start being cycled ready for new fish? I've got some Milton sterilising solution that we use for winemaking, would that be a good idea if I rinsed well afterwards? Or is there some specialist fish-safe tank cleaning product that I should be using?
All suggestions gratefully received!

OP posts:
EauRouge · 06/04/2014 17:18

Don't use Milton. Bleach is fine if it's diluted ten parts water to one part bleach, and then rinse it several million times (if you can get it under a shower it makes it easier). New gravel is a good idea. If you've got fake plants then they can be washed in the same weak bleach solution. I'd also rinse the filter in the bleach solution and get new sponges for it. Hope that helps!

How big is the tank? What sort of fish were you thinking of getting?

6 months is nothing, I left a tank empty for 18 months because I kept changing my mind about what to get Grin

grendel · 07/04/2014 11:13

Thanks for the advice eaurouge. I won't use Milton!
Just a bit nervous of using bleach. The tank is pretty big (about 90 litres or so) so is difficult to move, so massive amounts of rinsing are rather awkward.

I could use a weak bleach solution for plastic plants etc though as they are easy to rinse. I've rinsed and rinsed the gravel in water so it's now all fresh-smelling and shiny - do you think a weak bleach solution on that would be OK to kill off any potential nasties or would I be foolish not to buy new?

Thanks for suggestion re: the filter. I was dithering about whether it was better to reuse the sponge as presumably still has some good bacteria in there versus the worry that it could also harbour something unpleasant. Will start again from scratch.

Any advice re: fish? We only had the two goldfish by accident, don't particularly want to replace them. Instead we would like some small shoaling fish to give plenty of movement and interest. Ideally something not too fragile! Also how many could we comfortably have in our tank do you think?

OP posts:
EauRouge · 07/04/2014 11:30

Hmm, I've never cleaned up gravel with bleach so not sure. You can use playsand in fish tanks and it's dead cheap.

The filter sponges won't have any good bacteria left, it dies off pretty quickly once there's no fish and/or if you switch off the filter. You'll need to do a fishless cycle with the new sponges in to get it ready for fish.

90 litres isn't big enough for goldfish but there are loads of other fish that stay small. If you keep it room temperature then white cloud mountain minnows or zebra danios are the right size (you could keep a shoal of up to 10 of one or the other) and maybe a bristlenose plec, or if you add a heater then there are tons of small tropical fish to choose from. It's not more complicated to keep tropicals, it's just trickier to get the right ones because there's so much choice.

EauRouge · 07/04/2014 11:31

Argh, link fail. Here.

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