Fishless Cycle

[Fro]

Hello,

looking for some advice. I’m a newbie attempting a fishless cycle. I have a fluval 250l tank with fluval 307 filter. I dechlorinated the water. Added tetra safe start and am now feeding using dr Tim’s ammonia. After 5 days of following dr Tim’s instructions closely I’ve seen the ammonia go up after each time i add it but never down. Tank reading a small amount of nitrate but no nitrite. Ph is 7.6. Is patience the best bet here? Should I continue to add ammonia every few days as per dr Tim? What happens after the end of dr Tim instructions I.e. 2 weeks

[Aiken Drum]

You arent going to cycle a tank in 2 weeks. These products make exaggerated claims to get you to buy them. This is much more likely to take 8 weeks than 2 weeks. The quickest ive seen someone on this forum cycle a tank without using already cycled filter material is 3 weeks, someone recently did it in 4 weeks. Those are both unusually quick. 6 to 8 weeks is typical.

Ill post a thorough method of doing a fishless cycle that clearly outlines when to redose ammonia and a couple of tips that "might" speed things up from several months to several weeks.

But yes. Patience is key and not going into things with unrealistic expectations.

[Aiken Drum]

To cycle a tank you need to grow denitrifying bacteria to consume ammonia and nitrite that your tank produces. The bacteria needs an ammonia source to grow colonies sufficient in size to consume all the ammonia and resultant nitrite and turn it into nitrate which typically you remove through your regular water changes.

A fishless cycle uses an ammonia source to replicate the fish waste that a tank of fish would produce. This ammonia source can be pure ammonia, an aquarium specific ammonium chloride product like Dr Tims Ammonium Chloride, a cocktail shrimp or fish food.

Ill assume we are using an ammonium chloride product.

Set up your tank. Make sure everything is running smoothly. Make sure you have used a water conditioner product with any tap water you have put in your tank. If you have an adjustable heater raise the temperature to 28c/82.5f.

You should have a test kit. Preferably a liquid test kit. It should test for ammonia, nitrite, and nitrate.

Dose the ammonia chloride to approx 4ppm and start testing daily for ammonia. Once your ammonia drops below 1ppm redose it back to 2ppm. This may take a couple of weeks.

Start to test daily for ammonia, nitrite and nitrate. Whenever your ammonia drops below 1ppm redose it back to 2ppm.

You should start to see nitrite and possibly nitrate in your daily tests. Over time your nitrite should start to rise and the amount of ammonia should start to drop further. Your ammonia may start to not be detectable in your daily tests. Keep redosing ammonia daily if you see it below 1ppm. Your nitrite may rise off the testing chart. I prefer to keep nitrite within measurable levels so it shouldn’t hurt to do a water change to keep readings on the chart. Remember to add water conditioner whenever you put tap water in the tank. Nitrate should appear in your water test at some point too.

Over time your nitrite should level off and begin to fall in a similar manner to what your ammonia tests did. When you are able to dose ammonia to 2ppm and 24 hours later see 0 ammonia and nitrite you are cycled. At this point you have enough denitrifying bacteria to consume all the ammonia and nitrite of a moderately stocked tank. You may want to continue dosing ammonia for a few days to make sure it continues to consume all the ammonia and nitrite and be sure your cycle has properly established before proceeding.

Your nitrate will likely be very high. Do a big water change to get nitrate down. Preferably below 10ppm. Adjust your temperature to the needs of your fish. Get your fish, acclimate and add to your tank. I would advise stocking lightly to start with and slowly adding fish until fully stocked.

A fishless cycle typically takes 6 to 8 weeks.

A good way to speed up this process would be to put a small amount of filter media from an established filter into your filter, or get a sponge from an established filter and squeeze it into your tank water. Perhaps you have a friend who keeps fish who could let you have some? This will seed your filter with the bacteria you are trying to grow and speed up the process.

Another option is bottled bacteria like Dr Tims One + Only or Tetra Safestart. These products wont instantly cycle a tank as they claim but in a similar manner to adding established filter media they can seed your filter with the bacteria you are trying to grow to establish your cycle. These products are hit and miss as to whether they work at all, but are an option if established filter media isnt obtainable and may speed up the process from several months to several weeks.

[Fro]

Thanks for the detailed reply. Happy to wait it out for now. Will the tank not get dirty over this length of time? How often should I do water changes?

[Aiken Drum]

You dont "need" to do any water changes during a fishless cycle.

It depends on what you mean on dirty. You are dosing ammonia which is toxic for fish, but you dont have any fish. Doing water changes will just remove the waste that you need in the water to fuel the cycle, so you would end up having to redose ammonia to replace what you removed.

If you overdose on ammonia you may need to bring it down with a water change. Ammonia above 6ppm is commonly cited as being too much and will kill the bacteria you are trying to grow.

You may want to keep your water parameters to readable levels, so if for instance, your nitrite gets too high for your test to read you may choose to change some water to bring it down to a readable level. This isnt really needed, but might be something you want to do so you can see more easily whats going on.

The nitrogen cycle uses up carbonate hardness (KH) to convert ammonia into nitrate. Once its gone your cycle can stall. If you have low KH in your tap water you may need to replenish KH and a water change is one way to do this. But this is rare and unless you have reason to believe your water is low in KH i wouldnt worry about that just yet.