Ppm V's Mg/l When Water Testing

[TubbyLaLa]

Hi All,
Just got our first tropical tank and we are beginning a fishless cycle. We got the tank second hand and it had been used for a year and as the previous fish vacated the tank the day i picked it up I was lucky enough to inherit a mature filter. Have been reading the very useful posts on here but came across a small stumbling block, all my water testing kits read in mg/l rather than parts per million. Now I am a bit dizzy sometimes (have already replied to a four year old post in here ) so I don't want assumption to be the mother of all mess ups. Is 5ppm equivalent to 5.0mg/l or 0.5mg/l? Tanks is currently at 0.5mg/l of ammonia as I thought i could always add more but would have a harder job taking it away! And if this low level meant cycling took longer then so be it - we would like our fish to be as happy as possible when we eventually get them. Any advice greatly appreciated on everything, as the pet shop advised a single silver shark straight away in our small think about 10 Gal (took 42 litres to fill it) 2ftx1ftx1ft Tank. (Thank goodness I had done my homework on here first!!)
Many Thanks
Mrs TubbyLaLa

ETA Google search reackons 1ppm =1mg/l kinda makes sense like that or would take forever for bacteria to grow!

 

[rdd1952]

ppm and mg/l may not be exactly equal but are so close that they are considered the same. So your .5 mg/l isn't enough toreally cycle the tank. If you got a matue filter, the cycling should not take more than a couple days unless the filter dried out or went without ammonia too long and the bacteria died off.

 

[nckate]

1 L of water weighs 1 kg (or really really close), so 1 mg/l = 1mg/kg = 1 ppm.

... I love the metric system.