frothhelmet
Member
I'll just post this here for posterity. I spent several years trialling Theodoxus Fluviatilis shipments from Germany until I finally cracked the Theo code. Here are the rules for success.
1. There must be ample 'smearing' algae in the tank OR your tank must get some direct sunlight (which is the same thing)- or your Theos will die as there is NO WAY to feed them deliberately. Don't try to drop any food in the tank to feed them. It won't work. Theos are not attracted to prepared foods, even algae wafers, though they do seem to be able to 'smell' where the algae is on your glass. Most people 'think' they have ample smearing algae in their tank, but they do not. The only surefire way to succeed is to have direct sunlight hit your tank every day. I kept mine in a southfacing window and they kept all smearing algae at zero. Never had to clean to the glass, and I mean never. They will even clean Anubias of the dreaded green-spot algae that nothing else will remove - except other nerites. I did need an amano in the tank though to eat the staghorn algae that grew in the light. One way to keep Theos without direct sunlight, is to grow algae rocks in a sunlit tank and transfer them periodically to the Theo tank.
2. The water should be Ph >7 or the shell will corrode. However I have kept and bred them Ph <7 (high 6's), but only without CO2. When you put them in soft non-CO2 injected water, initially the shell will corrode until there is no pattern and only white left. But if they have ample food they may still successfully breed, at which point their offspring largely retain the pattern on their shell even in soft water and keep breeding for you. Therefore it appears that they can adapt to softer water if they are bred in it. So this is possible to do, but may take an acclimatization generation or so. The times when I put them in a CO2-injected tank they would just pucker their foot - see below.
3. They can be kept in tropical temperatures - but don't overdo it - they handle intermittent periods of 30C fine (like a couple days) but I killed them in >34C water before. In July 2020 we had 2 solid weeks of 30C weather and maybe 50-70% of my population died, but not all of them. Better to keep them below 27max - except for short periods.
4. Do not add ANY snails that will compete for algae - especially the egg-laying ramshorns and pond snails. Theos breed SLOW (like it will probably take you a full year to go from 6 to enough that you don't have to clean your glass anymore). Most other snails will outcompete your Theos for food and babies over time, and will gradually bring your Theo population to zero. Once you have Theos you have to be vigilant about what you put in the tank, making sure there are no snails or snail eggs on it. As it turns out, the live-bearing snails do not outcompete the Theos in my experience, so I have kept them fine with Malaysian Trumpet Snails (even with huge populations of these) and Tylomelanias. Algae eating fish such as SAEs also do not outcompete the Theos.
5. If ever they detach from the glass and 'pucker' their little foot, this is a sign they are not happy. They have not died but are weak due to either insufficient algae or too acid/soft water. These snails are not dead yet, but they will be in a few days or weeks. They will probably reattach to the glass if you help them, but if you don't correct the problem they will be dead soon. This is your warning sign. If they ever do this I remove them from the offending tank immediately and into better circumstances and they usually recover.
MISC INFO. Yes, they really do breed in full freshwater. What's more, their little white eggs do not leave unsightly casings when they hatch like the big brackish nerites in the hobby, but dissolve completely - so they don't ruin your decor. Which to all us low-tech scapers is a huge plus. They also stay small (like 1cm max) and their shells are super variable in pattern. When you move them into different tanks their new shell growths often start to look different like a tree ring. They ship super poorly, like once shipping times hit 3+ days you may get 100% losses, especially in warm weather. Don't ship if daytime temps will exceed 20C or if the weather could be below 4C (freezing will kill them too of course). Another interesting tidbit- they breed a bit throughout the year, but have a huge egg-laying bonanza at the end of spring / early summer. For some reason you will almost never see very small babies in their tanks (only saw one recently after keeping them for 10+ years), only juveniles.
1. There must be ample 'smearing' algae in the tank OR your tank must get some direct sunlight (which is the same thing)- or your Theos will die as there is NO WAY to feed them deliberately. Don't try to drop any food in the tank to feed them. It won't work. Theos are not attracted to prepared foods, even algae wafers, though they do seem to be able to 'smell' where the algae is on your glass. Most people 'think' they have ample smearing algae in their tank, but they do not. The only surefire way to succeed is to have direct sunlight hit your tank every day. I kept mine in a southfacing window and they kept all smearing algae at zero. Never had to clean to the glass, and I mean never. They will even clean Anubias of the dreaded green-spot algae that nothing else will remove - except other nerites. I did need an amano in the tank though to eat the staghorn algae that grew in the light. One way to keep Theos without direct sunlight, is to grow algae rocks in a sunlit tank and transfer them periodically to the Theo tank.
2. The water should be Ph >7 or the shell will corrode. However I have kept and bred them Ph <7 (high 6's), but only without CO2. When you put them in soft non-CO2 injected water, initially the shell will corrode until there is no pattern and only white left. But if they have ample food they may still successfully breed, at which point their offspring largely retain the pattern on their shell even in soft water and keep breeding for you. Therefore it appears that they can adapt to softer water if they are bred in it. So this is possible to do, but may take an acclimatization generation or so. The times when I put them in a CO2-injected tank they would just pucker their foot - see below.
3. They can be kept in tropical temperatures - but don't overdo it - they handle intermittent periods of 30C fine (like a couple days) but I killed them in >34C water before. In July 2020 we had 2 solid weeks of 30C weather and maybe 50-70% of my population died, but not all of them. Better to keep them below 27max - except for short periods.
4. Do not add ANY snails that will compete for algae - especially the egg-laying ramshorns and pond snails. Theos breed SLOW (like it will probably take you a full year to go from 6 to enough that you don't have to clean your glass anymore). Most other snails will outcompete your Theos for food and babies over time, and will gradually bring your Theo population to zero. Once you have Theos you have to be vigilant about what you put in the tank, making sure there are no snails or snail eggs on it. As it turns out, the live-bearing snails do not outcompete the Theos in my experience, so I have kept them fine with Malaysian Trumpet Snails (even with huge populations of these) and Tylomelanias. Algae eating fish such as SAEs also do not outcompete the Theos.
5. If ever they detach from the glass and 'pucker' their little foot, this is a sign they are not happy. They have not died but are weak due to either insufficient algae or too acid/soft water. These snails are not dead yet, but they will be in a few days or weeks. They will probably reattach to the glass if you help them, but if you don't correct the problem they will be dead soon. This is your warning sign. If they ever do this I remove them from the offending tank immediately and into better circumstances and they usually recover.
MISC INFO. Yes, they really do breed in full freshwater. What's more, their little white eggs do not leave unsightly casings when they hatch like the big brackish nerites in the hobby, but dissolve completely - so they don't ruin your decor. Which to all us low-tech scapers is a huge plus. They also stay small (like 1cm max) and their shells are super variable in pattern. When you move them into different tanks their new shell growths often start to look different like a tree ring. They ship super poorly, like once shipping times hit 3+ days you may get 100% losses, especially in warm weather. Don't ship if daytime temps will exceed 20C or if the weather could be below 4C (freezing will kill them too of course). Another interesting tidbit- they breed a bit throughout the year, but have a huge egg-laying bonanza at the end of spring / early summer. For some reason you will almost never see very small babies in their tanks (only saw one recently after keeping them for 10+ years), only juveniles.
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