Help, the Internal filter in my Juwel Record 70 has come loose. How can I fit it securely without emptying tank??. Ive lost two fish that have swam behind there and not go out. I have an Eheim external but want to keep the internal filter too if possible, rather than buy a new internal. Will silcone work underwater.?

Any advice greatly received, Presently the filter is loose in tank as I don't want to create a dangerous crevice.

Silicone won't work in water. I'm afraid you will have to drain the tank, dry thoroughly and then silicone it in. You'll need to wait 48 hours after that or the silicone to cure before refilling.

Also be careful that the silicone doesn't contain anti-mould ingredients ie NOT these - http://www.ebay.co.uk/bhp/anti-mould-silicone

Might be best to buy it from a fishkeeping retailer.

There are specialist aquarium silicones available which are fish safe, they would be the best option. Juwel and King British both make it, and both are available in small tubes which is great if you only need a small amount and don't want to buy a huge cartridge. I use the King British stuff for doing repairs to ornaments and artificial plants and it seems pretty good.