TDS, GH and KH test kits for shrimp tanks
Shrimp molt to grow, and successful molts depend on minerals in the water. That makes GH (general hardness: calcium and magnesium) and KH (carbonate hardness: buffering) the two numbers shrimp keepers test most, with a TDS meter as a quick daily check. Here is what each tool measures, according to its maker, and where owners say it falls short. We have not lab-tested these kits ourselves.
| Tool | Measures | How it reads | Strengths | Limits |
|---|---|---|---|---|
| API GH & KH Test Kit | GH and KH | Liquid titration: count drops in a 5 ml sample until the color changes; 1 drop = 1 degree | No upper limit; widely recommended by owners over strips | 1-degree resolution is coarse for very soft Caridina water; easy to lose count |
| HM Digital TDS-3 | Total dissolved solids | Digital, 0–9990 ppm, 1 ppm resolution under 1000 | Fast; ±2% accuracy (0–5000 ppm) per maker; automatic temperature compensation | Doesn't tell you which minerals are present |
| sera GH test / KH test | GH or KH (sold separately) | Liquid drop test | Common in Europe; includes syringe and chart | Same 1-degree drop resolution as API |
| Test strips (multi-parameter) | GH, KH, pH and more | Color match | Cheap and quick | Owners and reviewers repeatedly report vague readings and capped ranges; not ideal for shrimp |
Why TDS isn't enough on its own
A TDS meter reports a single number for everything dissolved. As Shrimp Science points out, 107 ppm could be the right GH for bee shrimp, or it could be almost all carbonate with zero GH, which would cause failed molts. TDS is most useful as a stability check after you've confirmed GH and KH, and it works best with remineralized RO water, where you know what you added.
Typical targets
Commonly cited hobby ranges, not hard rules:
- Neocaridina: GH about 6–8, KH about 2–6, TDS roughly 150–300 ppm.
- Caridina (bee shrimp): GH about 4–6, KH 0–1, TDS roughly 100–160 ppm, usually on active soil with RO water.
A simple routine
- Test GH and KH of your source water once, and again whenever your water supply changes.
- Test the tank's GH and KH weekly while it settles, then monthly.
- Check TDS at every water change; a sudden jump means something changed.
Keep a log so you notice slow drift. Our printable water parameter log is designed for exactly this.
GH, KH and TDS in plain English
GH (general hardness) measures dissolved calcium and magnesium. Shrimp draw on these minerals to build new exoskeletons, so GH that's too low is commonly linked to failed molts, and GH far too high is also cited as a molting problem.
KH (carbonate hardness) measures carbonate and bicarbonate, which buffer pH. Higher KH keeps pH steadier and generally higher; very low KH allows pH to drop. Caridina keepers aim for near-zero KH on active soil; Neocaridina keepers usually prefer a little.
TDS (total dissolved solids) is an estimate of everything dissolved, calculated from electrical conductivity. It can't tell calcium from sodium or fertilizer, so it's a stability check, not a substitute for GH and KH tests.
How to choose a test setup
- Keeping Neocaridina on tap water: a liquid GH/KH kit is the key purchase. A TDS meter is helpful but optional.
- Keeping Caridina on RO water: a TDS meter becomes much more useful because you control what goes in. Many keepers remineralize RO water to a target TDS and confirm GH with a drop test.
- Also cycling a new tank: you'll need ammonia, nitrite and nitrate tests too, usually in a liquid "master" kit.
- Budget-conscious: drop tests last for many tests per bottle. Strips cost more per test over time and are widely reported as less precise.
Using a TDS meter correctly
- Rinse the probe in the water you're testing, then dip it to the marked depth and wait for the reading to stabilize.
- Compare readings over time in the same tank rather than comparing to other people's numbers, since meters and conversion factors vary.
- Check calibration occasionally with a calibration solution if your meter supports it; HM Digital says the TDS-3 is factory-calibrated and can be adjusted.
- Expect TDS to rise slowly between water changes as minerals and waste accumulate and water evaporates.
Remineralizing RO water
Caridina keepers often start with RO (reverse osmosis) or distilled water, which has almost no minerals, and add a shrimp-specific remineralizer. Products differ in what they add. GH-only products raise calcium and magnesium without adding carbonate, which suits Caridina on active soil. GH/KH products such as SaltyShrimp Shrimp Mineral GH/KH+ raise both; SaltyShrimp states a GH:KH ratio of about 1.0:0.45 and suggests about 2 g per 10 liters to reach roughly 6 °dGH. Products like this are aimed at Neocaridina and other shrimp from neutral-pH habitats.
The usual workflow is to mix the remineralizer into RO water outside the tank, check the TDS, and confirm GH with a drop test before using the water for changes. Once you know what TDS your recipe produces, the meter becomes a quick check on each new batch.
Reading drop tests without guesswork
The color change at the end of a titration can be gradual. Owners suggest holding the tube against a white background, comparing against a tube of untested water, and counting the last drop only when the color has fully switched. If you're unsure, run the test twice. Because each drop equals one degree, the result is always a whole number: a tank reading 5 could be anywhere from about 4.5 to 5.5. Some keepers double the sample volume to halve each drop's value, which effectively improves resolution. Check your kit's instructions before trying this.
Common mistakes
- Relying on TDS alone. The right TDS with the wrong mineral mix can still cause molting problems.
- Topping off evaporation with tap water. Evaporation leaves minerals behind, so topping off with mineral-rich water drives GH and TDS steadily upward. Many keepers top off with RO or distilled water instead.
- Using expired reagents. Liquid test reagents have expiry dates printed on the bottle. Old reagents can give misleading results.
- Making big corrections at once. Sudden parameter changes are often cited as stressful for shrimp. Adjust gradually over several water changes.
- Not shaking reagent bottles. Some kits instruct you to shake certain bottles before use; follow the leaflet.
FAQ
What GH and KH do cherry shrimp need?
Commonly cited ranges for Neocaridina are roughly GH 6–8 and KH 2–6. They're adaptable, so consistency usually matters more than hitting an exact number.
What TDS is good for crystal red shrimp?
Hobby references commonly suggest roughly 100–160 ppm for bee shrimp on remineralized RO water. Check that GH is in range too, since TDS alone doesn't confirm mineral balance.
Are test strips accurate enough for shrimp?
They give a rough idea, but owners and reviewers frequently report vague color matches and limited ranges. Liquid drop tests are the common recommendation for GH and KH.
How often should I test my shrimp tank?
More often while setting up or after changes, then less often once stable. Many keepers test GH/KH monthly and TDS at every water change.
Why does my TDS keep rising?
Evaporation, fertilizers, food and waste all add dissolved solids. Topping off with RO or distilled water and regular partial water changes keep it steadier.
Do I need a pH test for shrimp?
It's useful, especially for Caridina on active soil, but GH and KH explain more about why pH is where it is. Many keepers test pH alongside them.
Our take
The API GH & KH liquid kit plus an inexpensive TDS pen like the HM Digital TDS-3 is the combination owners recommend most often. Skip strips for shrimp.
Sources: API GH & KH Test Kit instruction leaflet; HM Digital TDS-3 specification page; sera GH test product page; Shrimp Science, "TDS for shrimp tanks"; SaltyShrimp Shrimp Mineral GH/KH+ product page; Modest Fish test kit comparison (2024); r/shrimptank discussion (2024–2026). Checked October 2026.