I have a 55 gal tank that was freshwater that i switched to saltwater 9 months ago. I read that a freshwater tank is thinner tempered glass and may not stand up to the weight of the saltwater, live sand, live rock and could give way. should i be worried? it's been o.k for 9 months. I found this in my area 75 gallon Aquarium saltwater setup Is this a good deal? are there any questions i should ask the seller first?