Biopellets can strip your water of nutrients very quickly , ... And this shocks the corals and disrupts the di nitrification system in your current setup assume live rock as your main source.
There are many ways to achieve a smooth transition to low nutrient system. To try and explain in simpler terms ,... Leave the clever explanations to the experts - in a high nutrient system , you have allot of growth on your rocks like algue many you cannot see it but it's there.... When you start biopellets on a system your effectively rapidly removing the nutrients from the water colomb and naturally the flora dies as no more food, and releases those stored nutrients back into the water colomb. That's also why you will see many people who use a form of carbon dosing don't have any Caroline algue or very little, basically biopellets stave or out compete the algue for food. This release of nutrients is what creates the issues , old sandbeds are even worse and will drastically pollute your tank from the die off in the sand and there corpses effect your water quality hence effecting the livestock. This is natural as the new bacteria will colonies the biopellets as its basically a food source for the bacteria, hence most will also agree the outlet of the biopellets reactor would be direct or as close to the intake of your oversized skimmer, to remove excess bacteria growing on your biopetts ,.. This die off can manifest in many forms eg ,... Cyno Bacteria over population new algue etc ...
Most like me will tel you it's easier to start a new tank with biopellets than switch an established reef. There are many that have been successful with the transition , most pellet suppliers , will give you directions to slowly introduce the pellets based on your size tank,... In my opinion I cut that in half and double the time .... Slower is better. I would also recommend that you slowly remove your sand bed if it's old and also depending on what sand and depth . Deep sand bed will cause you endless problems ... Removing the sand bed is a different topic and requires some reseach from your side , don't just scoop it out ,... And may not be nessesery depending on depth etc.... Also don't pay that much attention to the quantity of pellets as every tank is different, and it depends on your feeding bio load etc etc , ... Quantity provided by the manufactures are more a guideline. Some have double The manufacturers recommendation coz they like fat fish and over feed, some have less but increase the flow or use a recirculating reactor to increase contact time...biopellets in my opinion is more about the user than the quantity and reactor type etc etc ... I have seen a biopellets reactors that also has air stones to oxaginate the water for more bacteria growth in super large systems.
In the end if done properly and methodically , the results speak for themselves and you won't look back.
Hope this helps you decide,.... There are many that will help you if you decide to switch , reactor and pellet type play a important role in switching many opinions and many success stories , best to listen to all and choose the best that suits you and your maintenance schedule.
