Aquatic ponds and rock gardens: water and stone features that have to keep working.

Algal growth driven by nutrients, sunlight and stagnation. The controls are shading part of the surface with planting, keeping nutrient input down through limited feeding and stocking, circulation and aeration, and adequate filtration for the volume. Chemical dosing treats the symptom and usually returns.

Unless the site has genuinely impermeable soil, yes: commonly a flexible membrane on a protective bed, or a concrete construction, with the water balance calculated for evaporation and top-up. Unlined ponds on permeable ground consume large volumes of water quietly and are a recurring cost nobody budgeted.

Regular skimming and debris removal, filter cleaning, pump checks, water-level top-up, periodic desilting, and management of the aquatic planting. Frequency depends on tree cover around it and stocking. Water features are among the highest-maintenance landscape elements and should be adopted knowingly.

Through gradual edge profiles rather than vertical drops, shallow marginal shelves, non-slip surfaces at approach points, planting or railing that limits direct access where depth requires it, and clear sight lines for supervision. Depth in publicly accessible ponds is kept to what the function needs.

A stagnant, unmanaged pond can. Circulation and aeration, avoiding still shallow margins with dense algal cover, and a healthy population of larvivorous fish where appropriate address it in practice. A designed and maintained water body behaves very differently from a neglected one.

Stone that looks bedded into the ground rather than set on it, with consistent geology and orientation, free drainage through the profile, and species suited to shallow, sharply drained pockets: succulents, hardy perennials and appropriate native material. Poor drainage and stone placed on the surface are what make rock gardens look artificial and perform badly.