Over the years we have had very good luck with old school floating hydrometers. We also like to use refractometers. Whatever you use, you should test them on a regular basis.
FYI: We have the old school floating hydrometers in stock for $9.99. They are only $8.00 for Maast members !

We also have the Red Sea 34 gal Max for $450.00. These come in black or silver. We also have the matching stands for $100.00. In the future, I will try to find time to post notice of more great prices.

H. Taylor
Aquarium Designs
15223 San Pedro
San Antonio, TX 78232
(210) 495-7333