Why this decision matters more than any other
A poorly installed pond costs far more to fix than it did to build. Inadequate filtration, wrong depth, improper liner installation, under-specified pumps — these problems compound over months and years. The difference between a great installer and a mediocre one is often $5,000–$20,000 in remediation work.
12 questions to ask every installer
- What filtration system are you specifying? They should be able to name the mechanical, biological, and UV components separately, with brand and model.
- What is the filter's rated capacity, and how does that compare to the pond volume? It should be at least double the pond volume.
- How many koi ponds have you built in the last 12 months? Pond building is a specialised skill. A landscaper who builds one or two ponds per year is not the same as a dedicated pond contractor.
- Can I see 3–5 ponds you've built that are at least 2 years old? Young ponds look good. Older ponds reveal the quality of the filtration, waterproofing, and construction.
- Will the pond have a bottom drain? For a dedicated koi pond, yes is the only acceptable answer.
- What liner or membrane specification are you using? EPDM should be minimum 1mm (ideally 1.5mm). Concrete specifications should include reinforcement details.
- What is your warranty on the waterproofing, and who backs it? You vs the liner manufacturer matters.
- Do you include aeration independent of the waterfall pump? If the pump fails overnight, fish can suffocate. Independent aeration provides safety backup.
- Who will be doing the actual work — your own employees or subcontractors? Quality control varies significantly.
- What's included in your quote for electrical work? Electrical should be done by a licensed electrician with permits. Some builders cut corners here.
- What support do you offer after installation? Phone support for the cycling period, at minimum. Ideally a structured follow-up visit.
- Can I speak to 2–3 recent clients directly? Not just read reviews — actually speak to them. Ask about the experience 12 months on, not just on completion day.
Red flags to watch for
- !Cannot explain what type of biological filtration they're using or why
- !Quote significantly lower than others — usually means something important is excluded
- !Unwilling to provide references or photos of older completed projects
- !Pushes you toward a decision before you've read their quote carefully
- !Cannot answer specific questions about filtration sizing or liner specification
- !No mention of the nitrogen cycle or pond cycling period
The key insight from SolarQuotes' model applied here: use one written brief for every installer. State your required filtration specification, depth, construction method, and fish stocking plans explicitly. Any installer who quotes below that specification is quoting a different product — and their lower price is not a saving.
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