Ever feel like your aquarium has a mind of its own? In this episode of The Aquarist’s Edge, we dive into the strange and puzzling phenomena that leave even seasoned aquarists scratching their heads. From vanishing fish to ghost algae that appear and disappear mysteriously, we're uncovering the science and offering real solutions to ten of the most bizarre aquarium mysteries.
Whether you’re haunted by cloudy water, dealing with plant meltdowns, or wondering how snails invaded your tank overnight, this episode delivers deep insights with practical advice.
* Mentioned in this episode: What Is Biofilm?
[00:00:00] Welcome to this episode of The Aquarists Edge, a podcast for home aquarists just like you. Learn more about how to keep a thriving aquarium and discover ideas and tips to give your aquarium the edge. And now, over to our host, Arthur Preston.
[00:00:22] Today we're going to crack open the case on some of the strangest, most baffling and seemingly unexplainable things that happen in our home aquariums. You know, those kind of head scratches that make you pause and go, hang on, what just happened here? Why do fish just seem to vanish without a trace? How does algae suddenly appear, disappear and then come back again? Why do your water parameters go haywire after months of stability? These are some of the mysteries we'll tackle today.
[00:00:52] We're going to look at 10 in total, each with a clear science-backed explanation and practical advice to help you solve or even prevent them from happening again. As always, I want to remind you as we get going that it would be wonderful if you could leave a comment or a review on your podcast app. Or if you're watching this or listening to this on YouTube, if you would like and subscribe to the channel.
[00:01:17] It helps us to grow, it helps us to spread the message and to keep people involved and interested in this amazing hobby. So let's get into mystery number one, the vanishing fish. One of the most unsettling mysteries for any aquarist is when a fish vanishes. You know what it's like, you do a head count and a couple hours later or the very next day you find that there's something missing. No signs of illness, no obvious distress and worst of all, no body.
[00:01:47] Well, obviously fish don't just disappear. But the conditions in a tank can lead to situations where a missing fish is practically invisible or quickly decomposed. Small species such as neon tetris or guppies can be consumed by scavengers within hours. Their bodies are soft and once they're dead, they become targets for snails, shrimp and various bottom dwellers. Even medium-sized fish such as dwarf cichlids can vanish overnight if the tank is heavily stocked.
[00:02:17] Jumpers are another big culprit. Labyrinth fish such as bettas and garamis and surface skimming fish such as hatchet fish can jump when startled. And sometimes their bodies are hard to find. You need to be looking behind stands, under furniture, in nearby pop plants. Check your tank for small crevices or filter gaps where a fish may wedge itself and perish. Use your feeding time as a behavioural check. Missing fish during feeding are often a red flag.
[00:02:47] And again, it goes back to what you've heard me say a number of times. Watch your fish. Spend time at your tank. Observe. It's amazing what you can learn. So how do we stop this? Well, it's always a good idea to cover your tank with a secure lid, to perform regular head counts and use a feeding routine to keep tabs on fish activity. And if a fish does go missing, check for filter intakes, look behind decor and under driftwood. Mystery 2.
[00:03:16] Algae that comes and goes like magic. You know what it's like. You'll come into your aquarium. You'll spend some time scrubbing away the algae. Enjoy a few days of crystal clarity. And then what do you know? It's back. Green fuzz or brown film or thread-like strands. Algaes follow nutrient availability and light exposure. So when conditions are right, algae spores, which are always present, bloom. When conditions change, they crash.
[00:03:45] This is particularly common with diatoms, green spot algae and green dust algae. Diatoms love silicates and are common in new tanks. Green dust algae often colonise glass when phosphates are high. And black beard algae appears when carbon dioxide levels fluctuate. So what causes this cycle? Well, there's overfeeding, which can lead to phosphate and nitrate buildup. Inconsistent lighting. Inconsistent lighting. And water changes that remove nutrients that plants rely on.
[00:04:14] And this gives algae the edge in your tank. Some solutions would be to keep a stable lighting schedule. To use a timer and avoid direct sunlight. To test the nitrate and phosphate levels regularly. To introduce algae eaters such as autosynchrist, neurite snails or siamese algae eaters. And consider dosing fertilisers consistently for planted tanks to avoid imbalances. And that's a good idea. Mystery number three. The phantom ammonia spike.
[00:04:45] You're religious with your maintenance. You haven't changed your feeding or stock level and yet your test kit shows ammonia. What gives? Well, a sudden ammonia reading often points to a disturbance in your biological filtration. Beneficial bacteria live primarily in your filter media. Cleaning too vigorously with tap water can kill them due to chlorine and temperature shock. A decaying organism such as a dead snail under the substrate can also cause a spike.
[00:05:13] Another hidden factor might be the use of medication. Antibiotics or copper-based meds can impact your biofilter. Similarly, overuse of dechlorinators such as Prime can temporarily bind ammonia which will confuse your test kit. The way around this is to make sure that you are cleaning your filter sponge and media in removed tank water only. Not under the tap but in tank water.
[00:05:40] You can also check for dead tank mates in hard to see areas. Avoid stirring the deep gravel unless absolutely necessary. And it's always a nice idea to keep a backup sponge filter running to re-establish bacteria if needed. Mystery number four. Cloudy water with no clear cause. Your water has gone cloudy overnight. Milky white or just a dull grey.
[00:06:09] Now most often this is caused by a bacterial bloom. These blooms are fuelled by excess organic material. Often after a large water change, substrate stir or overfeeding. They're not dangerous but they're ugly and they can indicate imbalance. In new tanks, this bloom is part of the nitrogen cycle. In established tanks, it can be triggered by adding new substrate or cleaning filters too aggressively.
[00:06:36] Other culprits include an improperly rinsed substrate, leaching from driftwood or decor, or an overpopulation of microfauna or infusoria. A solution would be to reduce your feeding temporarily, to increase surface agitation to oxygenate the water, to avoid additional cleaning and let the bacteria stabilize, and only use fine filter floss or water clarifiers in an emergency. Before we get into the next half of this list of aquarium mysteries,
[00:07:06] I want to let you know that this is episode number 50 of the Aquarius Edge podcast. It is season two, but it is number 50 in the list of all the podcasts that we've put out. I've decided that each season would be related to the year in which they're produced. So season one was the podcast episodes in 2024, and season two are the podcast episodes from 2020. In total, episode number 50 is this one.
[00:07:36] I want to take a moment to thank you for listening to the podcast. I want to thank those who have been listeners from the very beginning, those who have shared the podcast with others, and those who continue to be regular and loyal listeners. Thank you for spending time with me every week as we dig into more about what it means to be a successful home aquarist. I'm really grateful for your support. Thank you. And let's continue to push forward. And I'm looking forward to the next 50 episodes so that in a few months time,
[00:08:06] we can celebrate 100 episodes of the Aquarius Edge. And now let's move on to the next number of mysteries in our home aquariums. Mystery number five, The bubbling sand bed. Now this is when tiny bubbles emerge from the substrate like a bit of a miniature spa. This is usually harmless nitrogen gas, produced when denitrifying bacteria in anaerobic zones reduce nitrate to nitrogen.
[00:08:33] It's a sign of deep biological activity. However, if your sand is too deep and compacted, hydrogen sulfide can develop, which is a toxic gas and it smells like rotten eggs. How do you know the difference? Well, nitrogen bubbles are odourless. They frequent and can appear during cleaning or when fish dig in the substrate. Hydrogen sulfide smells bad, rotten eggs, and often accompanies black patches in the substrate.
[00:09:03] The way to prevent this is to keep your sand beds under five centimeters, unless they are designed for deep anaerobic use. To stir lightly with a chopstick during water changes or some kind of gentle stirring. And to consider animals such as Malaysian trumpet snails that gently turn over the substrate on a regular basis. Mystery number six, Fish acting drunk or disoriented. They're listed sideways,
[00:09:33] they're swimming circles, or they're just floating around the tank oddly. And this wasn't from a bender the night before. This comes from swim bladder disorders, toxins such as aerosol sprays or paints or contaminated hands that have gone into the tank, sudden parameter shifts, especially pH or temperature shock, or low oxygen due to poor surface agitation or overcrowding. And the solution for this is to perform an immediate water change if you suspect toxins are in your water, to increase aeration with air stones or surface agitation,
[00:10:03] and always wash your hands before tank maintenance. You can so easily introduce something into your tank that is poisonous to the tank inhabitants without even realizing it. So get into the habit of either washing your hands regularly before you do your tank maintenance, or wear gloves. Mystery number seven, and this is one I think many of us have experienced quite often, and that is snails reproducing out of nowhere. Tiny snails appear, and within weeks,
[00:10:32] your tank is snail city. So most often these are pest snails, such as pond snails or bladder snails. Their eggs can chike on plant leaves or decal. They multiply rapidly in tanks with excess food or decaying organic matter. Best way to prevent this is to quarantine and rinse all new plants with bleach. Just the normal bleach, dip them for a bit, wash off the bleach afterwards, and then you can use them. Reduce feeding to limit snail reproduction.
[00:11:02] You can add snail predators, such as assassin snails or loaches. And you can use traps, basically with some kind of food lettuce or zucchini or something like that that you put into the snail trap, algae tabs, things like that overnight. And I will do an episode at some point on creating your own DIY traps. They're not difficult to make, and they are very effective. Mystery number eight. What about, let's call it mold,
[00:11:32] growing on driftwood? You've added beautiful driftwood that's cost you a fair bit of money into your tank, and now it's covered in white fluff. There's no need to panic. This is simply harmless biofilm, a colony of bacteria and fungus feeding on organic matter in the wood. It's part of the breakdown process, and it's particularly common with new or soft woods, such as mapani. In fact, I've actually done a podcast episode on the slimy stuff in your aquarium,
[00:12:01] which is all about biofilm. And if you happen to be listening to this on YouTube, I will put a link to this on the video screen. You'll be able to click on it on the top right, and I'll put a link to that episode in the podcast description. How do you deal with this? Well, you can manually remove it with a siphon during water changes. You can add a wood-eating fish such as plecos or shrimp. Shrimp love biofilm. It's a staple diet for them. They absolutely love it. And it will typically clean up on its own within two to six weeks.
[00:12:30] No need to panic at all. Mystery number nine. Sudden pH swings. Your once stable tank is now acidic, and your fish are stressed. And this often points to low KH, which is carbonate hardness, which buffers the pH. As biological processes produce acids, a low KH tank can quickly drop in pH. And a CO2 injection system can also cause pH dips if not regulated.
[00:12:59] So test your KH regularly. You could add crushed coral, some kind of other organic matter to stabilize your tank and avoid large sudden water changes with drastically different pH. And finally, number 10, the last of the mysteries for this episode, melting plants. You've added beautiful new plants. You've enjoyed going to go to your local aquarium shop and you've spent some money on some stunning plants. You plant them in your tank
[00:13:28] and within a day or two, they start to go brown. They start to look very insipid. It actually looks like they're melting. Now, most aquarium plants are grown immersed, which means above water. When submerged, they must grow entirely new leaves adapted to underwater life. And this causes the old growth to melt away. Poor nutrient levels, a lack of CO2 or inadequate light can exacerbate this issue, making recovery slow or at times even impossible.
[00:13:58] You need to trim off the melting plants, trim off the parts of those plants to prevent rot. You can dose with root tabs or liquid fertilizers. Make sure that you've got adequate lighting for the specific species of plant and be patient. Many plants will bounce back very healthily after two to four weeks. Well, folks, there you have it. Ten aquarium mysteries decoded and explained from disappearing fish to ghostly algae and spontaneous snail invasions.
[00:14:28] we've now learned the truth behind these strange occurrences. Just remember that most of these phenomena are rooted in science and can be managed with the right knowledge and tools. Now, if you've got a mystery we didn't cover, let us know. Put a comment on the YouTube video, send us a message, write us an email at admin at artsfisherm.co.za That's admin at artsfisherm.co.za And let us know. Maybe we'll feature that in a future episode. In the meantime,
[00:14:57] until we meet again for episode 51, keep learning, keep discovering, keep enjoying this amazing hobby. Take care. See you next week. Bye for now. That's it for this episode of the Aquaris Sedge. Please consider subscribing to this podcast so that you don't miss further episodes. We would love it if you would also rate and review the podcast as this helps make it visible to others. Until next time, keep learning and discovering and keep finding
[00:15:26] your Aquaris Sedge in this captivating and fascinating hobby.