Sorry just noted your cats get bullied, So you will have problems finding what you need, suggest re-stock with more temperate fishes, all the best Mike, London.ps i used to live in Brisbane.

I have always found the bronze coryadoras to be a very busy cleaner for the gravel but you will be best served to pay a visit to your local aquarium to find some cats that have the habit of sticking to the glass sides and buy a couple of those, That way you get the bottom and sides of the aquarium ...