Hey everyone. I thought I would pass along some of the instruments I use for my indoor hydroponic grow. The 3 things I use the most that I got great deals on are my TDS meter, PH meter and a mini microscope. (See Ozone Generator a few posts down) TDS Meter: TDS Meter $15.95: http://cgi.ebay.com/HM-Digital-TDS-3-Meter-PPM-Hydroponic-Water-Tester_W0QQitemZ350167486917QQcmdZViewItemQQptZHydroponics_Seed_Starting?hash=item350167486917&_trksid=p3911.c0.m14&_trkparms=72%3A1205%7C66%3A2%7C65%3A12%7C39%3A1%7C240%3A1318 Features: Hold function allows you to keep the data on the screen you want to record. Factory calibrated in a 342ppm NaCl solution. Meters can be re-calibrated with a small screwdriver if users wish. Digital Thermometer is built in. Batteries INCLUDED AND INSTALLED. Auto Turn Off Function turns off after 10 minutes of no use. Advanced Microprocessor Technology makes for an amazingly accurate device. Great for professional or personal use. Specifications: TDS Range: 0 ~ 9990ppm (mg/L) Temp. Range: 0 - 80 degrees Celsius Resolution: 1 ppm, 1 degree Celsius (also available in 10 ppm) Accuracy: +/- 2% ATC: Built-in sensor for Automatic Temperature Compensation of 1 to 50 degrees Celsius (33 to 122 degrees Farenheit) Power source: 2 x 1.5V button cell batteries (included) Battery life: over 1,000 hours of continuous use Dimensions: 15.5 x 3.1 x 2.3cm (6.1 x 1.25 x 1 inches) Calibration: Factory calibrated. Weight with case: 76.5g (2.7 oz) Package Contents: Brand New MH Digital TDS Meter Carrying Case Product Manual Installed Batteries PH Meter: Ph meter $24.99: http://cgi.ebay.com/pH-Meter-Digita...5|66:2|65:12|39:1|240:1318|301:0|293:1|294:50 Testing pH level has never been to so easy! You are bidding on a brand new professional-grade pH meter with LCD display. It is design for aquariums, swimming pools, fish hatcheries, laboratories, paper industry, food processing, and etc. With a built-in automatic temperature compensation system (ATC), this pH meter is accurate and very easy to use. Features Built-in ATC (Automatic Temperature Compensation) Compact, light weight and mobile Super accurate for measuring - Aquarium - Swimming Pool & Spa - Laboratory & Hospital - Winery & Nutrient - Hydroponics - All Water Applications Easy to use - Turn on the unit, dip, stir and read - that's it! User's manual included Specifications Measuring range: 0.00 to 14.00 pH Accuracy : Â±0.1 pH (at 20 C) Calibration: manual, 1 point Environment: RH 95% max; 32- 122F (0- 50 C) Batteries: 3x1.5V alkaline Dimensions: 5.9"x1.2"x0.8" (152mmx30mmx31mm) Mini Microscope: MiniMicroscope $9.99 http://cgi.ebay.com/60x-100x-Lighted-Mini-Microscope-XUK1-7545_W0QQitemZ110296759930QQihZ001QQcategoryZ11704QQtcZphotoQQcmdZViewItemQQ_trksidZp1713.m153.l1262 A precision illuminated microscope with adjustable 60x-100x magnification. Can be used with the stand like a large microscope, or without it. Focus can be adjusted by turning the wheel. Countless uses for hobbyists, collectors, electronic engineers , scientists, and students. It is about 6 1/2 inches in height. Includes 2 AA Panasonic batteries. This is fantastic for looking at the thrichs. You get a great upclose look. I can see through some of the clear ones!!