Restarting a Vitii pool in spring: analyze, mineralize, restart the biofilter (complete guide)

The first mild days arrive, the water warms up, and your Vitii pool emerges from winter. This is the most important time of the year for a bio-mineral pool. A properly managed restart, in three stages - analyze and mineralize, restart the biofilter, then clean and check the consumables - prepares a whole season of clear water. A rushed restart will come back to haunt you in June with cloudy or green water, just when you want to go swimming.

Why spring is decisive for a bio-mineral pool

A Vitii pool is not disinfected: it is balanced. Its water stays clear because a bacteria-populated biofilter breaks down organic matter, because phosphorus is kept too low for algae to thrive, and because a precise mineral balance stabilizes the pH and promotes the precipitation of unwanted elements. During winter, cold water slows the bacteria down. In spring, algae often start growing again faster than they do.

The whole challenge of restarting is to give the bacteria the advantage again before the algae gain theirs. It's a race, and it is won in the first weeks of the water warming up, not in June.

Step 1: analyze and mineralize

The first step is to analyze the water. You have three options: the Vitii test kit, a Spintouch-type photometer, or the Aqualyser analysis counter at a partner retailer. Measure at least the pH, KH (or TAC, carbonate hardness), GH (or TH, total hardness), and phosphates.

The KH/GH ratio, the core of the system

The biomineral principle is based on a ratio between carbonates and minerals. Divide your KH by your GH: the result should be between 0.5 and 0.75. Example: with a KH of 6 °dH and a GH of 10 °dH, the ratio is 0.6, so you are within the target range. With a KH of 4 and a GH of 12, the ratio drops to 0.33: the carbonates need to be raised.

A few biologist's rules for correcting without going off track:

• Split the additions: add part of the calculated dose, let the water circulate for twenty-four hours, then measure again. Hardness should never be corrected all at once without risking cloudiness or pH drift.
• Correct hardness before pH: KH buffers pH. Adjusting pH in poorly buffered water means having to start over the next day.
• Take winter rainfall into account: rainwater contains very few minerals. After a wet winter, hardness levels have often decreased through dilution.
• Follow the dosages indicated by Vitii for your volume: they are the authoritative ones.

Step 2: restart biological filtration

Once the mineral balance has been reached, and only then, the biofilter is reseeded. The added bacteria then find a stable environment in which to establish themselves instead of being subjected to pH fluctuations. Two products work together:

• Bactostart provides a starter bacterial population that recolonizes the filter media and resumes the breakdown of organic matter.
• Anti-phosphates lowers available phosphorus precisely when algae are trying to restart. For a few weeks, it gives the bacteria time to catch up.

Leave the filtration running continuously during this phase. The flow brings food and oxygen to the attached bacteria. Turning off the pump at night to save energy in spring is the mistake that costs the most in summer.

Step 3: checking the consumables

A Vitii pool uses four automatically dosed liquid consumables: Bacteri for the bacterial flora, Calci and Carboni for mineral balance, and Citri for pH. Before the season, check the levels, hoses and injection connectors, which may become clogged or cracked over the winter.

Pay particular attention to the Bacteri bag-in-box. It is a living product: once opened for more than six months, it loses its effectiveness. A container opened in July of last year must be replaced in spring, even if some remains. Injecting dead bacteria is equivalent to injecting nothing at all.

Step 4: cleaning up winter residue

Leaves, pollen and fine deposits have accumulated on the bottom over the course of several months. They are a source of phosphorus that will feed algae as soon as the weather warms up. Vacuum the bottom, clean the walls and poorly circulated areas, and empty the skimmer and pre-filter baskets.

If the pool is heavily soiled or the water is cloudy, Vitii offers treatment products: Bio-Clear, which combines flocculation and enzymatic degradation of organic matter, and Bio-Cleaner for mechanically cleaning surfaces. Slightly lowering the pH with pH- may improve the effectiveness of biological treatment products: follow the brand's instructions and measure again before making adjustments.

The typical schedule

1. Day 1: cleaning, restarting the pump and equipment, and initial analysis.
2. Days 2 to 5: gradual correction of KH and GH, with daily measurements.
3. As soon as the ratio is between 0.5 and 0.75: Bactostart and anti-phosphates.
4. Following week: check the pH, inspect the consumables and automatic dosing.
5. Then: a complete analysis every one to two weeks during the season.

The mistakes that ruin the season

• Adding bacteria before correcting the mineral balance.
• Waiting for the first heatwave to start up.
• Keeping an expired Bacteri “because there is some left”.
• Repeatedly correcting the pH without checking the KH.
• Treating green water with a chemical algaecide that also destroys beneficial flora.

Also read

For more information about filter flora: Bacteria in natural swimming pools and constructed wetlands: which ones should you use?

READ THE ARTICLE

Frequently asked questions

— When should I restart a Vitii pool?

As soon as the water warms up consistently in spring, before the algae get ahead. Better too early than too late.

— What KH/GH ratio should I aim for?

A KH divided by GH ratio between 0.5 and 0.75.

— My Bacteri has been open since last year; can I finish using it?

No. Once opened for more than six months, it loses its effectiveness: replace it.

— The water is green when starting up, what should I do?

Clean, restore the mineral balance, lower phosphates and restart the bacteria. Avoid chemical algaecides that destroy beneficial flora.

In summary

• Test first: pH, KH, GH and phosphates.
• Aim for a KH/GH ratio between 0.5 and 0.75, making small adjustments.
• Then restart the biofilter with Bactostart and a phosphate remover.
• Check the four consumables and replace any Bacteri that is more than six months old.
• Clean out winter deposits before the first swim.

Last updated: September 28, 2026.