TDS Levels in New Jersey - What is Safe in Reef Aquariums?
If you are keeping a reef aquarium in New Jersey, water quality is everything. Your corals, fish, and invertebrates rely on the purity of the water you use, and one of the most telling measurements of that purity is TDS, or Total Dissolved Solids.
Whether you’re a seasoned reefer or just getting started, knowing TDS, what it is, why it matters, and what’s acceptable for a saltwater tank could be the difference between a thriving reef and a frustrating battle with algae, pests, and dying coral.
What is Total Dissolved Solids (TDS)?
Total Dissolved Solids is a measurement of all dissolved material in your water that is not H2O. Water has a tendency to pick up all kinds of things as it moves through soil, pipes, treatment plants, or filtration systems. All of these add up to the TDS.
In terms of practice, TDS comprises:
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Inorganic Salts
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Calcium
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Magnesium
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Potassium
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Sodium
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Chloride
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Sulfates
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Bicarbonates
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Heavy metals – lead, copper, iron, and zinc, often leached from aging pipes
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Typical byproducts of agricultural runoff and water treatment are nitrates and phosphates
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Silicates - a major contributor to the diatom (brown algae) blooms that plague new reef tanks
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Chloramines and chlorine – disinfectants added in municipal treatment
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Organic compounds - pesticides, herbicides, and trace pharmaceuticals
TDS is measured in parts per million (ppm) or milligrams per litre (mg/L).
Why TDS is so important in a reef aquarium
The biology of a reef tank is very fragile. Corals, particularly SPS (Small Polyp Stony) corals like Acropora, are among the most chemically sensitive organisms you can keep. Even trace contaminants can cause common coral diseases, bleaching, tissue necrosis, or death.
This is why high TDS is so dangerous in a saltwater tank:
Nitrates and phosphates: These promote nuisance algae and cyanobacteria, hinder coral calcification, and compete with the beneficial bacteria in your live rock and sand bed. In a high-end SPS reef, 0.03 ppm of phosphate is considered high.
Silicates: Particularly infamous for causing diatom blooms, that rusty-brown film that covers your sand, glass, and rocks, especially in a newly established tank. Most local hobbyists are quite frustrated by the high silica content in New Jersey tap water.
Chloramines: A combination of chlorine and ammonia used in New Jersey municipal water. Chloramines are more stable than plain chlorine and don't dissipate on their own. They are toxic to fish and invertebrates. They can destroy the beneficial bacteria that your biological filtration relies on.
Heavy Metals: Even at very low concentrations, heavy metals are acutely toxic to invertebrates, especially crustaceans and molluscs. Copper, present in many New Jersey water supplies due to aging plumbing infrastructure, is deadly to most invertebrates at very low concentrations.
Unidentified Compounds: Perhaps the most concerning element of TDS is the unknown compounds. It does not tell you what is in the water, only that there is something there. “You don’t know if that 30 ppm is silicates, phosphates, or arsenic,” many experienced reefers say. The danger is the unknown.
TDS Levels in New Jersey Tap Water
Water quality in New Jersey’s municipal water systems varies widely by region and water supplier. The state relies on both surface water reservoirs and groundwater aquifers, and the mineral content reflects that diversity. In places like Rockaway, Dover, and Madison, tap water has been measured to have TDS levels ranging from moderate to relatively high, usually between 100 and 400 parts per million, but sometimes higher, depending on the source and time of year.
New Jersey also uses chloramines in most of its municipal supplies instead of plain chlorine, which standard activated carbon filters can’t remove entirely. This is a critical distinction for reef keepers.
What is safe to drink is not safe for your reef. New Jersey tap water, with a properly operated municipal supply, contains silicates, phosphates, trace metals, and chloramines in quantities that can cause serious trouble in a reef aquarium.
What Is The Safe TDS Level In A Reef Tank?
The answer is simple and almost unanimous in the reef-keeping community:
The TDS target for your water going into your reef tank is 0ppm.
In practice, 1-2 ppm is generally accepted as okay, and many seasoned hobbyists will use water up to 5 ppm without much concern. But for SPS-dominated tanks or very sensitive systems, anything above 1 ppm should cause you to pull over and investigate.
There is a bit more tolerance for LPS (Large Polyp Stony) corals and softies (soft coral) tanks. Some hobbyists have healthy LPS systems with source water reading up to 10 ppm, but the closer you are to zero, the fewer variables you introduce.
The key insight here is that TDS is measured on the water that is going into the tank before salt is added. Once you mix in reef salt, the conductivity and dissolved content of the water skyrocket; you cannot use a TDS meter to test saltwater. This measurement is for your pure, purified source water only.
How to Get 0 TDS: RO/DI Systems
The best way to make water for a reef aquarium is from a Reverse Osmosis/Deionisation (RO/DI) system. That two-step process is what separates the serious reefers from the frustrated ones, particularly in a state like New Jersey that has relatively high tap TDS.
Reverse Osmosis ( RO ) uses pressure to push tap water through a semi-permeable membrane that rejects 90-98% of dissolved solids. Tap water that was 250-350 ppm might read 8-15 ppm after a RO membrane. Big progress, but not nil.
Deionisation (DI) is a second stage that uses an ion-exchange resin to capture the remaining dissolved ions, thereby reducing the output to 0 or 1 ppm. If your DI resin is fresh and functioning properly, you should always read 0 ppm on your meter.
A quality 4-stage RO/DI unit typically consists of:
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Sediment pre-filter (removes particles and sediment)
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Carbon block filter (removes chloramines, critical for New Jersey water)
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RO membrane (rejects the bulk of dissolved solids)
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DI resin stage (polishes the water to near-zero TDS)
Most experienced reefers will also install a dual inline TDS meter, one before the DI stage and one after, so they can monitor the performance of each stage and know when to change cartridges. The DI resin is considered exhausted and should be replaced when the post-DI TDS starts to creep above 1-2 ppm.
How to Measure TDS
TDS is simple and inexpensive to measure. A simple handheld TDS pen meter costs under $30-$55 and gives you an instant reading. Just dip the probe in your source water (pre-salt), press the button, and read the display.
The HYDROS Dual Inline TDS Meter attached to your RO/DI unit will provide you with live readouts from various points throughout the system to better monitor when membranes and DI resin need to be replaced.
A few tips for accurate TDS testing:
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Always test your source water before adding salt
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Calibrate your meter periodically using a calibration solution
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Test your post-DI water regularly, especially if your source TDS is high
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Keep records, seasonal changes in municipal water can shift your tap TDS noticeably
A Note to New Jersey Reefers
Anywhere you are in New Jersey, assume your tap water is not reef safe without treatment. Chloramine use, different water sources, and aging infrastructure mean TDS levels and contaminant profiles vary from town to town. The only way to know what is in your water is to test your own supply and then filter accordingly. Make sure you test any water bought from a local fish store with your own TDS meter before use.
Conclusion
Getting TDS right is one of the most impactful things you can do for your reef, but navigating RO/DI systems, test kits, and New Jersey's specific water challenges can feel daunting.
Whether you need equipment advice, testing kit recommendations, or ongoing maintenance support, the friendly Reefco Aquariums team is here to help you. We offer expert aquarium consultations specializing in reverse osmosis evaluation and TDS checks. Contact us today. Let’s talk water.
