Ah this is what I had imagined First things first, I suggest you up your pipe size for the supply to the filter and YOU WILL HAVE TO for the GRAVITY feed from the filter to the waterfall. The pump should take up to 40mm hose, NOTE hozelock hoses tails are metric in OD with an imperial 1.5"BSP thread. A lot of hose is still imperial, up to 1" metric=imperial but 32mm=1.26" and 40mm=1.57". Fitting 1.25" hose onto a 32mm is a wee bit of a struggle but 1.5" hose on a 40mm hosetail is a swearing match, it can be done and is best done by getting a piece of 40mm pushfit PIPE, not hose, and filing a 1 in 10 or 1 in 15 taper on one end right down to the bore of the pipe. Heat the hose with a hairdryer, £5 from argos, and twist the hose onto the pipe, the diagram below shows how to twist the pipe and hose so that the helix of the hose opens as they are twisted, if your helix is the other hand than swap the directions of rotation a little bit of plumbers silicon grease high up the taper will help. Once the hose is well on the pipe let it sit for a while to take a set. Cut of the smaller unused hosetails and file a slight taper on the hozelock hosetail. Take the pipe out using the same twisting action and fit the hose over the hose tail. Alternatively buy an Oase aquamax hose tail as that should fit. I normally use a Hozelock hose tail on an aquamax pump. Why do I say up your hose size, small bore pipe has a high resistance to flow. I have a hose "pipe loss" chart presumably form hozelock as it in metric It quotes the following losses for 25mm/1" hose 1591lph 5 cm per metre of hose 2273lph 10cm per metre of hose 2386lph 11cm per metre of hose???? 3409lph 21cm per metre of hose for 32mm hose 3409lph generates 7cm per metre of hose and 40mm hose generates about 3cm per metre of hose. I guess you know what follows but I include it for 'completeness'. The pump sees the friction as added lift and that cuts down the flowrat, you are paying for the wasted energy via your electricty bill. It is up to you whether you up the supply side but the return is a different kettle of fish, the head that pushes water from the filter to the fall is the drop in water level from the surface inside the filter to the surface over the water fall and that is finite. The hose connecting the filter and the fall isnt bothered by whether the flow is pumped or gravity driven, its resistance will be the same as listed above. So, say you have 8 ft of 1" hose and a flow rate of 2273lph you would require the level inside the filter to be 1.6ft, 19.2", above the level over the fall and at a guess more because that will be into the media which its self will add slightly to the required head. For you information, I am setting the plant pond up with a filter system, that will have gravity feed to a...

Its difficult to run a UV on lower power I guess, and I doubt a 12v pump would be up to much, only thing ya can get at 12v is pond lights.

Glad to hear other fish have survived this, thanks Alison, I am beggining to feel a bit better about this whole situation. I have added salt before with no real efect on the water plants so I feel that I am probably safe in that respect. The little pine cones are swimming around happily as if nothing is the matter with them so I am keeping fingers crossed as you would expect. As for pond size, it is 750 litres and the amount of salt i put in was probably the same as third a tea cup so in reality not too much to harm but enough to promote osmosis or whatever it is called. New filter has 50% of the older filter sponges and other media so that should help to balance them out a bit (thanks for that idea mark). Uv is switched on and now I am just waiting to see the water clear up. I have also raise the level of the pump slightly and also added about 2" more water to the pond just to be on the safe side of things. As for medifin, when should I add more, I did have the instructions but alas I put them in a safe place so I didn`t lose them!!

Hi PondNovice The 4500 for me has been ok so far. This is my 3rd summer and it has seen 2 winters. I hope I will not bombard you with info, but here goes.... Definely use pond water to clean the sponges as it reduces any determintal affect on the good bacteria within the filter. The fresh tap water you have been using will contain chlorine which can kill the friendly bacteria. The bacteria forms a 'biofilm' or slimely coating on the plastic shapes right at the bottom of the filter below the sponges. Don't clean these bits of plastic, I think mine are blue. This will ensure the levels of toxic nitrites (given off as waste from fish) are converted to nitrates which the plants use as fertilizer. I might have got the -ites and -ates round the wrong way! long time since A-level biology! For maintence basicly buy a new full set of sponges every year ~£13-15, they clog up quicker the older they get. BE CAREFUL: There are 2 versions of bioforce 4500, they revised the model design slightly around 2001-2. The versions have different sponges with respect to the hole in the middle of them. I think the later version has a bigger hole to accomodate the UV section. Also, replce the UV light bulb every year. They only have a 12 month useful output. Keep the quartz housing clean hrough the summer as only 60% of the UV gets through a clean quartz so a coating of algea makes it almost not worth having it on. BE CAREFUL when changing the UV light bulb. My unit developed a leak in March when I changed mine. See my last post on this thread. The only reason I noticed I had a leak into the electrical wiring of the UV unit was the RCD device light. Which was off. I tried powering up but it kept flicking off. DEFINELY have a RCD for both the UV light and the pump or anything electrical that is in contact with the pond water. I could go on for ages. Please ask if anything is not clear. May the force be with you. Groan Mark