- Sku: 80300
- Vendor: Fritz
Fritz RPM Liquid PT 1 Alkalinity | 2-Part Alkalinity Supplement for Reef Aquariums
Fritz RPM Liquid PT 1 Alkalinity is part one of the Fritz Reef Pro Mineral two-part dosing system, formulated to replenish the alkalinity (KH) consumed by growing SPS, LPS, and soft corals. Made with pharmaceutical-grade ingredients in the USA, RPM PT 1 keeps your reef chemistry stable between water changes so corals can color up and skeletons can keep building.
Pair PT 1 with Fritz RPM PT 2 (Calcium) for full two-part dosing, and verify your levels with a precision Salifert KH/Alkalinity Test Kit or the Hanna dKH Alkalinity Checker. Browse the full additives & supplements collection for the rest of your reef chemistry lineup.
How It Works
Corals consume alkalinity (carbonate hardness) as they build their calcium-carbonate skeletons. As KH drops, coral growth slows, polyp extension diminishes, and stressed tissue can recede. RPM PT 1 delivers a balanced liquid alkalinity supplement that you dose daily — alongside RPM PT 2 (calcium) — to keep dKH steady inside the reef-safe range of 8.0–9.5 dKH.
Features — All Sizes
Choose Your Size — Variant Comparison
Select a size in the tab section below for the full individual spec sheet.
| Spec | 16 oz | 32 oz | 1 Gallon | 5 Gallon |
|---|---|---|---|---|
| Volume | 473 mL | 946 mL | 3.78 L | 18.9 L |
| SKU | 80300 | 80301 | 80303 | 80304 |
| Form Factor | Round bottle | Round bottle | Jug w/ handle | Bucket w/ handle |
| Ideal For | Nano / pico reefs | Small reefs 20–60 gal | Mid reefs 60–180 gal | Large / multi-tank systems |
| Works With Dosers | ✓ | ✓ | ✓ | ✓ |
Detailed Variant Specifications
Click a size below to view its full specification sheet.
16 oz · Nano-Reef Bottle · SKU 80300
The 16 oz bottle is sized for nano and pico reef hobbyists running tanks up to about 20 gallons, or for anyone who wants to trial RPM dosing before committing to a larger jug.
| Specification | Value |
|---|---|
| SKU | 80300 |
| Volume | 16 fl oz (473 mL) |
| Best for | Nano & pico reefs (≤ 20 gal) |
| Dispensing | Pour cap, manual or doser |
| Brand | Fritz Aquatics |
| Made In | USA |
32 oz · Small-Reef Bottle · SKU 80301
The 32 oz bottle is the everyday size for small reefs in the 20–60 gallon range. About double the dosing runway of the 16 oz with the same convenient bottle format.
| Specification | Value |
|---|---|
| SKU | 80301 |
| Volume | 32 fl oz (946 mL) |
| Best for | Small reefs (20–60 gal) |
| Dispensing | Pour cap, manual or doser |
| Brand | Fritz Aquatics |
| Made In | USA |
1 Gallon · Mid-Reef Jug · SKU 80303
The 1 Gallon jug is the sweet spot for the typical mid-sized reef tank (60–180 gallons). Best value per ounce for hobbyists running daily two-part doses with a peristaltic doser.
| Specification | Value |
|---|---|
| SKU | 80303 |
| Volume | 1 US Gallon (3.78 L) |
| Best for | Mid reefs (60–180 gal) |
| Dispensing | Carry handle, gravity-feed or doser pickup |
| Brand | Fritz Aquatics |
| Made In | USA |
5 Gallon · Large-System Bucket · SKU 80304
The 5 Gallon bucket is built for large reefs, frag systems, and multi-tank fishrooms. Months of dosing runway in one container; pulls comfortably with a stiff dosing tube and weighted strainer.
| Specification | Value |
|---|---|
| SKU | 80304 |
| Volume | 5 US Gallons (18.9 L) |
| Best for | Large reefs, frag tanks, multi-tank rooms |
| Dispensing | Sealed bucket w/ handle, dosing tube pickup |
| Brand | Fritz Aquatics |
| Made In | USA |
Which Size Is Right for You?
16 oz — Pick this for pico/nano reefs (≤ 20 gal), or to trial RPM dosing before stepping up.
32 oz — The everyday size for small reefs in the 20–60 gallon range.
1 Gallon — Best value for the typical mid-reef hobbyist running daily two-part doses on a 60–180 gallon system.
5 Gallon — The choice for large reefs, frag systems, and anyone running multiple tanks who wants months of runway.
How to Dose
Begin by testing your current alkalinity to establish a baseline. As a starting point, dose 1 mL of RPM PT 1 per gallon of tank water to raise alkalinity approximately 0.7 dKH — then adjust based on your daily consumption rate after running a 48-hour test sequence. Always dose PT 1 and PT 2 separately (different times of day, or different points in the sump) to avoid precipitation. Never combine them in the same dosing reservoir.
FAQ
Do I need to dose PT 2 (Calcium) at the same time?
Yes — RPM is a two-part system. Alkalinity and calcium are consumed together by coral skeletal growth, so dose roughly equal volumes of PT 1 and PT 2 daily, spaced apart by at least an hour to prevent precipitation.
What dKH should I target?
Most reef hobbyists target 8.0–9.5 dKH. SPS-dominant tanks often dial in tighter (8.5–8.8) and prefer rock-stable readings over high numbers.
Can I use this in a fish-only saltwater tank?
You can, but there's no need — fish-only systems don't consume alkalinity quickly. Weekly water changes with a quality reef salt cover everything a FOWLR tank needs.
Will PT 1 affect pH?
Yes — alkalinity supplements can nudge pH upward briefly after dosing. This is normal; the effect dampens as the buffer integrates into the system.
Is it safe for refugiums, sumps, and inverts?
Yes. RPM PT 1 is reef-safe when dosed at the recommended rate and is compatible with shrimp, snails, starfish, anemones, and macroalgae refugiums.
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Fritz RPM Liquid PT 1 Alkalinity | 2-Part Alkalinity Supplement for Reef Aquariums
