Highlights:
- Tank Water Needs Extra Care: Tank water can introduce organics, nutrients and metals — making your pool more prone to algae. Always pre-filter and test your tank water before adding it to your mineral pool.
- Keep pH And Alkalinity Balanced: Regularly check and maintain your pH between 7.2–7.6. This is critical for preventing algae growth and ensuring your sanitiser works effectively.
- Smart Acid Dosing: Only add acid when needed — typically 100–200 ml per 10,000 L for minor pH corrections. Always test, add in small amounts and retest after a few hours to avoid over-correcting. Never add more than 1,000ml per 50,000l pool in one dose.
- Algae Prevention Is Easier Than Treatment: Maintain good circulation, brush walls and steps weekly and use a mineral-pool-safe algaecide or phosphate remover to keep green algae from taking hold.
- Monitor After Weather Or Water Changes: Rain, storms and new tank water can all upset your pool chemistry. Test more often after these events to stay ahead of algae and pH drift.
How To Manage Green Algae And Get Your Acid Levels Right
Keeping a mineral pool clear can be a balancing act — especially if you’re topping up with tank water. In this post, we thank our long-time customer Melissa from Wynnum West, Queensland for her feedback and share expert tips to help manage green algae and get your acid levels just right.
Featured Testimonial
At Aquatune, we love hearing from happy customers — and this week, we want to give a big shout-out to Melissa from Wynnum West, Queensland who shared this glowing testimonial:
“Excellent service and delivery – even to QLD! Best shipping rates, fast and reliable. I am a repeat customer of several years now, easy to use website.”
- Melissa from Wynnum West, Queensland.
Thank you, Melissa! We truly appreciate your loyalty and kind words. Customers like you make it all worthwhile — and we’re always here to help with expert advice to keep your pool sparkling.
Melissa also asked a great question…
Featured Question
“What’s the best green algae management for mineral pools if using tank water — and how much acid is really needed weekly?”
Here’s our specialist advice 👇
You raised two excellent and related questions — so we’ll break it into two parts: (1) managing green algae in a mineral pool fed by tank water and then (2) acid dosing (to manage pH) in such a pool. The “mineral pool + tank water” scenario has a few additional considerations, so it’s good you asked.
1. Managing Green Algae In A Mineral Pool Using Tank Water
When you’re using tank water (often rainwater or stored water from a tank) for your mineral pool, you need to be especially vigilant because the water source may have variable quality (nutrients, organics, dissolved metals, etc) and may be more prone to algae if the chemistry isn't tightly controlled. As a result of run off from the roof and the environment, you may also have high phosphate levels (Algae food).
Here are tailored recommendations:
a) Ensure good circulation, filtration & brushing
Even with a mineral pool, good mechanical cleaning remains vital: skim frequently, brush walls/steps, vacuum where needed.
Keep your filter clean/backwashed so that fine algae and organic debris don’t linger.
Stagnation zones are ideal for algae growth, so ensure pump run-time and circulation cover all areas. Remember to brush low circulation or stagnate areas like steps and corners.
b) Control nutrient input & tank-water quality
Tank water can carry extra organics, leaves, dust, bird droppings, dissolved nutrients or metals – these things can sometimes leave high phosphate levels. These can fuel algae.
Make sure your tank is shielded from direct light where possible and remove debris entering the pool. (In general water-tank best-practice guides note that sunlight + nutrients accelerate algae growth).
If practical, use a fine pre-filter or run the tank water through a sediment trap before feeding the pool.
Always ensure that your pH is around 7.2-7.6. Remember the higher the pH, the lower the chlorine efficacy.
c) Maintain your mineral pool chemistry very carefully
It is important to check basic chemistry weekly (pH, alkalinity, calcium hardness etc) even though the sanitising mechanism may seem different, many types of chlorination increase pH over time.
Algae loves higher pH / higher alkalinity / higher nutrient loads. So keep your pH within the ideal range (usually ~7.2-7.6) and total alkalinity (TA) and calcium hardness in correct ranges for your system.
d) Use a suitable algaecide or preventive product
Green algae is one of the most common types. In this case, use an algaecide after shocking/cleaning to prevent recurrence.
In mineral pool systems, although the sanitising mechanism is somewhat different (magnesium/chlorine‐ion based etc) you still can use algaecides compatible with that system (check manufacturer’s specs!).
Also consider “phosphate removers” (phosphates fuel algae) especially if your tank/trade water might be high in phosphates or organics.
A regular maintenance dose of an organic algaecide may be wise to consider.
e) Maintain your sanitiser residual
Even though it’s a mineral pool (less chlorine perhaps than standard pools), you still need to ensure adequate sanitiser residual so algae can not take hold. Many mineral pool systems rely on a lower chlorine residual but combined with minerals.
If you see a green tint or start of algae, the first response is to shock, brush, vacuum and then add algaecide – don’t wait as timing is crucial. Lower the ph and add a shock dose (don’t add together though).
f) Monitor and adjust after heavy weather or load
After heavy rain, storms, large swim loads (kids, parties) your nutrient load and water quality can shift quickly. Tank water feed may also change (if the tank receives roof run‐off). So do a quick check and respond proactively.
2. How Much Acid Is Really Needed Weekly?
Acid (usually hydrochloric acid or similar) is used primarily to lower pH (and sometimes total alkalinity) when they drift too high. The amount you need depends on many factors: pool volume, current pH/TA/calcium levels, how much water you’re adding (tank‐water feed), bather load, rain, evaporation, etc. There is no, one-size-fits-all “X ml per week” rule but we can give guidance and a rule-of-thumb + specific considerations for your scenario.
a) Typical guidelines
For standard pools: if pH is 7.6–7.8 in a 10,000 L pool you might add ~500 ml of hydrochloric acid (HCl) to bring it down.
Every pool is different so test regularly with some quality home test strips (not the ones from the supermarket).
b) What to check weekly
- Measure pH (target ~7.2-7.6 for comfort and sanitiser efficiency).
- Measure total alkalinity (TA). High TA can buffer pH and make acid dosing harder.
- Calculate your pool’s volume (litres) – you’ll need this for accurate dosing.
- Check how much tank water you're adding each week (fresh water tends to raise pH/TA or lower it depending on source).
- Note weather, swimming load, debris input (all affect pH drift).
c) Rule‐of‐thumb for your scenario (mineral pool + tank water)
Given you have a mineral pool and are using tank water, we’d suggest:
Weekly check and dose only if needed: e.g., if pH >7.6, add acid; if it’s stable at ~7.4-7.6, you may not need to dose every week.
If your pH is looking high, add a litre (assuming average pool volume of 50,000l) then test again after 4 hours of circulation.
Important: add in smaller increments rather than one big dose, test after 4 hours and then adjust. This avoids over-correction.
d) Other factors when using tank water
If your tank water has higher pH or TA than your pool, adding that water will tend to shift your pool pH/TA upward (meaning you might need more acid).
Conversely, if your tank water is soft or low in alkalinity it might cause your pool to become more aggressive and you might need to raise calcium hardness rather than acid. So test the tank water as well.
If you are adding large volumes of water regularly (tank top-ups), the chemistry shift could be significant and you’ll need more frequent checks (maybe twice a week).
e) Safety & good practice
Always follow manufacturer’s instructions on the acid bottle. Use correct safety gear (gloves/eye protection) because acid is corrosive.
Never add water to acid; always add acid to water (in a bucket) then disperse around the pool.
After acid addition allow pump running, test again after 4 hours before letting swimmers in.
Putting It All Together – Your Maintenance Checklist
Here’s a summary checklist tailored for you:
- Weekly: Test pH, total alkalinity (TA), calcium hardness (since mineral pool), sanitiser residual.
- If pH is >7.6 – 7.8 → add acid (say start with ~100-200 ml per 10,000 L, adjust based on pool size/TA).
- When adding tank water: test that fresh water (pH, TA) to anticipate its effect.
- Maintain sanitiser residual appropriate for your mineral pool system so algae can’t take hold.
- Use an algaecide (compatible with your mineral system) especially as preventive if you notice any green tint or recurrence risk.
- Keep circulation, filtration, brushing consistent. Remove debris, cover pool when not used if possible, minimise nutrient input from tank water or surroundings.
- After heavy rain, large swim sessions or big tank-water additions: check more often (e.g., 2-3 times that week) and respond quickly.
- Consider a regular maintenance dose of an organic algaecide.
Final Thoughts
Using a mineral pool with tank-water feed is absolutely manageable and many owners do it with great results. The key is consistent monitoring, controlling nutrient and algae entry points and staying on top of your chemistry (especially pH & acid dosing). If you keep your pH in the ideal zone, sanitiser residual solid and minimise nutrient load (especially from the tank water), the green algae risk will greatly reduce.
We’re delighted you’re part of the Aquatune family and appreciate your years of loyalty. If you’d like to discuss your exact pool volume, your mineral system brand or have data on your tank water (pH/TA) we’d be more than happy to help you dial in a more precise acid-dosing plan – just drop us a line.
Thanks again for your kind words, Melissa — enjoy your pool time and we look forward to supporting you for many more years!
The Aquatune Team
P.S. Do you have a question about your pool and or spa? Share it with us here and as a small token of our appreciation we will also send you a discount code for $10 off your next order over $75 (which includes free delivery)... https://www.aquatune.net.au/pages/quick-favour
P.P.S. Do you look after your pool or spa yourself? Join our Do-It-Yourself Pool and Spa Maintenance community here… https://www.aquatune.net.au/pages/diy