TDS Pen Water Tester
GENERIC_PEN_TDS_PEN_ESSENTIAL
A TDS pen is an inexpensive handheld digital meter that measures total dissolved solids (in ppm) to gauge overall water quality and mineral content. It is essential for monitoring RO/DI...
Or build it into a bundle — save up to 6% ↓What it is, and who it is for.
A TDS pen is an inexpensive handheld digital meter that measures total dissolved solids (in ppm) to gauge overall water quality and mineral content. It is essential for monitoring RO/DI filter output, checking tap water, and tracking nutrient or remineralizer levels in planted and shrimp tanks. Pocket-sized with an LCD readout, most models read 0-9990 ppm with automatic temperature compensation; the representative unit shown is the HM Digital TDS pen.
Build around the TDS Pen Water Tester.
It's already in your system below. Add the flow, filtration and dosing around it and the discount starts working — tiers climb as the build grows, and the reef meter fills with it.
Pick the right one, not the biggest one
The honest line-up from test kits. Most buyers reading this page should buy the middle column.
Salifert Reagent Test Kit
TDS Pen Water Tester
RefractometerAsked before checkout
The questions our support inbox actually gets.
Does it ship quickly?+
Orders placed before 2 PM ET on a business day leave the same day. Tracking is emailed the moment the label prints.
What if it's the wrong fit for my tank?+
Return it. 30 days, no restocking fee, refund to the original payment method. Better: tell us your tank first and we'll spec the system for free — half of all returns are sizing problems.
Who handles the warranty?+
We do. Everything carries the manufacturer's warranty and we run the claim for you — one email to us instead of a ticket queue.
How does the bundle discount work?+
Add items in the bundle builder: 2+ items saves 5%, 3+ saves 8%, 4+ saves 12%, and 5+ saves 15% off the whole system, applied at checkout.