Pond Equipment for tanks?

I was at petsmart looking around for what ever reason and i saw "Pond Rid-Ich" i look and read, everything was same that mine said but this was 36 oz, and $2.50 and mine was 6oz for $4. It said add 1tsp for every 10gallon, etc salt-water and so on.

Now can u use that on a normal salt water tank? I have a reef tank so i wouldn't use it but curious.

Also i saw a 1000 Gallon Sump filter, it had everything mine had, Black foam, white ceramic circles, etc. also said "extra room to add more filter items!"

It was $149, whats the diffrence between that and my 75 gallon filter i paid $80 for (store closing got 50% off)

 

i read the page pond is the same thing just in a bigger package

petsmart probably just knocks up the price for aquariums because more people by that type then the bigger pond one.

as far as the filter unless it had metal in it was probably ok.

 

It was all plastic, would a 1000 gallon filter be extremely too much for a 55 gallon tank