Why Most Goldfish Die Young (And How to Fix It)
Goldfish have a reputation for being low-maintenance starter fish. In reality, goldfish are among the most demanding fish to keep long-term. They produce far more waste than tropical fish, need more oxygen, and require larger tanks than almost any beginner expects.
A single fancy goldfish produces waste equivalent to 3-4 small tropical fish. Without proper filtration and water changes, ammonia spikes within days — leading to fin rot, gill damage, and death within weeks. This is the number one killer of pet goldfish worldwide.
The good news is goldfish are incredibly hardy when given the right environment. Kept properly, common goldfish live 10-15 years. Fancy goldfish varieties typically live 5-8 years. Some pond goldfish have lived over 20 years. This guide will show you exactly how to give your goldfish that long, healthy life.
Tank Size: The Minimum You Need
The old rule of "1 inch of fish per liter" completely fails for goldfish. A single fancy goldfish needs at minimum 40 liters (about 10 gallons) of water, and a second goldfish needs another 20 liters on top of that. Common goldfish (the slim-bodied type sold at fairs) need even more — at least 75 liters for one fish, as they can grow 25-30 cm.
In Cambodia's warm climate, tank size is even more critical because warmer water holds less dissolved oxygen. A 20-liter bowl that might keep a betta alive will suffocate a goldfish within hours in 30°C room temperature water.
Tank shape matters too. Wide, shallow tanks hold more oxygen than tall, narrow tanks. A rectangular tank with a large surface area is better than a tall column aquarium. If you can only afford one upgrade for your goldfish setup, make it tank size.
- ✦Minimum 40L for the first fancy goldfish, +20L for each additional fish
- ✦Common/comet goldfish need 75L minimum — better suited for outdoor ponds
- ✦In Cambodia's heat, always add an air stone or surface agitation to boost oxygen
- ✦Avoid round bowl shapes — low oxygen exchange surface + no room for filter
Water Temperature and Parameters
Goldfish are coldwater fish, meaning they prefer 18-24°C. In Cambodia where room temperature often reaches 28-35°C, this is a significant challenge. You have three options: run an air conditioner in your fish room, use a small aquarium chiller (expensive but effective), or choose goldfish varieties that tolerate warmer water.
Ryukin, Oranda, and Ranchu goldfish handle temperatures up to 30°C better than Common or Comet goldfish. At temperatures above 30°C, all goldfish become stressed, stop eating, and become vulnerable to disease — especially the deadly goldfish herpesvirus (KHV) which activates above 28°C.
Water pH should be 7.0-8.0. Goldfish prefer slightly alkaline water. Ammonia must be 0 ppm, nitrite must be 0 ppm, and nitrate should be below 40 ppm. Test your water weekly, especially in a new tank that has not completed the nitrogen cycle.
- ✦Target 22-25°C if possible — use a fan blowing across the water surface to cool 2-3°C
- ✦Add crushed coral to gravel to buffer pH upward if it drops below 7.0
- ✦In Cambodia, daily evaporation can concentrate nitrates — top up with dechlorinated water daily
- ✦Never use Phnom Penh tap water directly — dechlorinate with sodium thiosulfate or commercial conditioner
Filtration: The Most Important Investment
Goldfish need heavy filtration. Plan for a filter rated at 8-10 times your tank volume per hour. For a 40L tank, you need a filter moving at least 320-400 liters per hour. This sounds excessive, but goldfish produce so much waste that a weaker filter will struggle to keep up.
Canister filters are ideal for goldfish tanks — they hold more biological media, run quietly, and are easy to maintain monthly. Hang-on-back (HOB) filters are the second choice. Sponge filters alone are not enough for goldfish tanks unless combined with another filter.
Never clean all filter media at the same time. The beneficial bacteria that convert ammonia to nitrite to nitrate live in the filter. Washing all media at once destroys the colony, causing an ammonia spike known as a "mini-cycle" that can kill your fish within days.
Feeding Goldfish Correctly
Feed goldfish small amounts twice daily — only what they can finish in 2-3 minutes. Overfeeding is the second most common cause of goldfish death after insufficient tank size. Uneaten food rots, spikes ammonia, and quickly turns a healthy tank toxic.
Goldfish pellets are better than flakes because they sink less slowly and create less surface foam. Sinking pellets are ideal for fancy goldfish with round bodies, as they prevent these fish from gulping air at the surface — a common cause of swim bladder disorder.
Supplement the diet 2-3 times per week with fresh vegetables: blanched peas (shell removed) are excellent for digestive health and prevent constipation. Other good supplements include blanched spinach, zucchini, and small pieces of watermelon. In Cambodia, young pennywort leaves (bai barang) are a great local supplement.
- ✦Pea treatment: blanch 1-2 frozen peas, squeeze out of shell, feed to constipated fish — works within 24 hours
- ✦Fast goldfish one day per week — helps prevent digestive issues common in fancy varieties
- ✦Store pellets in a cool, dark place — Cambodia's heat degrades vitamins in fish food quickly
- ✦Avoid flake food as the main diet — too much surface feeding causes air swallowing
The 5 Most Common Goldfish Diseases in Cambodia
Ich (white spot disease) is the most common goldfish disease and thrives in Cambodia's warm climate. Look for white spots the size of salt grains covering the body and fins. Treat with temperature increase to 28°C (to speed up the ich life cycle) combined with commercial ich treatment. Complete the full 7-10 day treatment cycle even when spots disappear.
Fin rot appears as ragged, darkened fin edges — caused by bacterial infection following stress or injury. Treat with clean water, daily 20% water changes, and antibacterial treatment. Melafix (tea tree oil extract) is widely available in Cambodia and effective for mild cases.
Swim bladder disorder causes goldfish to float at the surface or sink to the bottom. The most common cause in fancy goldfish is overfeeding or constipation. Fast the fish for 3 days, then feed blanched peas. If the problem persists, check your feeding volume and switch to sinking pellets.
Dropsy (pinecone disease) is the most serious — the fish's scales stand out like a pine cone due to internal organ failure. Isolate immediately, treat with Epsom salt baths (1 tablespoon per 4 liters), and antibiotic food if available. Dropsy often indicates permanent kidney damage — prevention through water quality is far more effective than treatment.
Anchor worm and fish lice are visible external parasites — you can see them with the naked eye on the body. Remove physically with tweezers (anchor worm) or a swab, treat the wound with antiseptic, and add potassium permanganate or commercial antiparasitic treatment to the tank.
Buying Goldfish in Cambodia — What to Look For
When buying goldfish in Cambodia, inspect the fish carefully before purchase. Healthy goldfish are active, have erect fins, clear eyes, no visible wounds, and no white spots or fuzzy patches. Avoid fish that are sitting at the bottom, gasping at the surface, or have torn fins.
Check the tank the fish came from — if other fish in the same tank are sick or dead, pass on the fish even if they look healthy. Ich and bacterial infections spread rapidly and an apparently healthy fish can be in the early stages of disease.
At 4848 One Shop, all our goldfish are quarantined for 7 days before sale and inspected for common diseases. We ship nationwide via VET Express with DOA guarantee — if your fish arrives dead or severely stressed, we replace it free.