Hi, have Bioforce Revolution 9000 kit which included Aquaforce 6000 pump bought Sept 2015 with 3 yr guarantee. Pump has now expired, diagnosed with very low electrical resistance...means nothing to me I’m afraid. Need to replace said pump....local fish place don’t stock HLock but have Pond Expert Ultraflow 5300 which they insist will do the job. They asked if pond was in full sun...it is for the most part, when it shines! I queried it’s lower through rate and was told I could overflow the pressurised filter if I went any higher...Never had any issues before and the kit has always worked fine. Can anyone please suggest which pump would be a good make to go with if I decide to swap brands. Is it right that Hoselock are upping the guarantee to 5 yrs please. Thanks in advance.