Gravel cleaning or bottom cleaning of tank

May I first introduce myself, I am 71 years old and a male, married
with two rescued dogs called Jack and Benjie. Recently I got interested
in keeping tropical fish which I very much enjoy but I do seem to have
problems in keeping the bottom of the tank clean, like what you see in
Aquariam stores. I use a syphon pipe but I do not fine this really
works very well and I have recently heard that it is possible to
purchase a mechanical vacum but as yet have no luck. Would be very
grateful if members could advise me. Regards to you all. John