My daughter's birthday has prompted a return to owning a fish tank. Its been 20 odd years since I last owned fish so I'm a bit rusty and probably had bad habits then anyway.

She wanted a goldfish bowl for her birthday, which I didn't want to get for obvious reasons. So I picked up a second hand biorb for her, and then another for me, since I know that I'll want to take over hers otherwise. I realise that they aren't hugely popular tanks, but it is perfect for me right now.

Hers is a 30L, mine a 60L. Mine has been 'helpfully' cleaned of filter and ceramic media. Hers has old media and filter, but left stagnent for a couple of months (its a bit brown now with algae on the heater etc).

Since I don't really know the history of either I'm sort of leaning towards cleaning both with diluted white vinegar solution, including the ceramic media, chucking the old sponge and basically starting from scratch. I can do this before her birthday.

I'm then (despite all the articles about fishless cycling) thinking of letting the tank run for a few days and then letting her get a single fish because she'll be climbing the walls by then and I'm sure we've all been there (she's going to be 7).

So my questions really reside around the best way to get the tank up and running asap. Should I run the BiOrb without charcoal to start with or just run it as Reef One instruct, for an easy life?

They do a sachet of dechlorinator with a bacteria add in, should I use that?

Any good tips? I used to keep cichlids years ago so I wouldn't mind tips of more suitable fish either.

Fishless cycle is a must - any fish put into an uncycled tank will suffer irritation and pain from the ammonia they create and may become sick and die. If they manage to survive while the tank cycles they will have permanent damage from living in their own waste.

30L Biorb is unfortunately too small for any fish but could be used for shrimps and/or snails.

I really can't echo the comment about "fishless cycle is a must" enough - it is fundamental to fishkeeping. The nearest analogy I can think of is the equivalent of buying a dog but, because there somehow isn't time to get/prepare the habitat for it or get it food, keeping it in torturous circumstances such as forced to stay in a cardboard box without exercise or food, all because the child might become impatient if s/he had to wait any longer. Probably not the best of analogies, especially as most other pets don't require the set-up/advanced preparation time that fishkeeping requires before the actual pet (fish) is purchased, but hopefully you get the drift.

Having said that, shrimps and/or snails (rather than fish) are ideal for the 30-litre Bi-Orb, as Fishlady says. Some are brightly coloured and they get up to all sorts of antics which can be just as engaging to watch as fish - my orange nerite snail is so clumsy, gets into the most awkward of positions and often ends up doing acrobatics such as catapulting backwards off tank decor, while I've read of others finding it amusing watching their shrimp hand-gliding from floating plants or stealing and running off with a piece of food from another.

Bi-Orbs aren't generally recommended for fish at all, even the larger one. With the possible exception of a Siamese Fighter Fish / betta, even the tiniest of fish species require a tank with a minimum 30x60 cm footprint and have very specific requirements - seriouslyfish.com provides details of individual species' requirements.

Hope that helps.

PS. Further thoughts: how about growing aquatic plants in the 60-litre Bi-Orb, and then, if you're still keen on fish, get the biggest tank you have space for (second-one ones are available via aquarist-classifieds.co.uk) and choose fish whose requirements are in line with what you can provide?

In a nutshell:
* 30-litre Bi-Orb: shrimps/snails which are visually/actively interesting (and spares the heartbreak associated with a fish-in cycle and/or kept in an unsuitable environment)
* 60-litre Bi-Orb: aquascape +/- shrimps/snails
* fishtank for fish (if space/finances permit)