Fish food life time in tank

[The endler guy]

can we get some sort of list or something detailing how long certain foods can stay in the tank before heavily affecting water quality (for scavengers or grazers for example) 

[anitstuk]

I'm pretty sure algae blocks for shrimp or algae eaters can last a while.. I haven't tried tho so don't take my word for it 

[TheSwissAquarist]

On 11/4/2022 at 6:38 AM, anitstuk said:

I'm pretty sure algae blocks for shrimp or algae eaters can last a while.. I haven't tried tho so don't take my word for it 

My plecos are still chomping down on algae blocks which are 2 years old (but then again, they eat everything!)

[The endler guy]

On 11/4/2022 at 2:41 AM, TheSwissAquarist said:

My plecos are still chomping down on algae blocks which are 2 years old (but then again, they eat everything!)

Good to hear! That definitely eases some stress about leaving them in

[Guppysnail]

On 11/4/2022 at 2:41 AM, TheSwissAquarist said:

My plecos are still chomping down on algae blocks which are 2 years old (but then again, they eat everything!)

You have had an algae block IN a tank for 2 years? Or are the blocks just 2 years old?

If I read the original post correctly it was how long after being put in a tank until they affect it. 
 

The answer to this question varies. It depends on your water lower ph may affect how quickly the food breaks down some start releasing nitrogen almost immediately. 
 

If there is a specific food you can place it in a cup of tank water and test at regular intervals for ammonia and nitrite. 
 

If it’s eaten or dissolved it’s still released as ammonia/nitrogen waste product. 
 

Cory did a video or livestream talking about vegetables I think explaining it doesn’t make a lot of difference if the fish eat it then the BB eats the waste or if the tank eats it directly. But you do want to remove leftovers before fungus and such grow. 
 

Hope that helps 

[TheSwissAquarist]

On 11/4/2022 at 11:31 AM, Guppysnail said:

You have had an algae block IN a tank for 2 years?

Of course not!! I have kept the algae block packet (its got a decent seal on it) for 2 years!

[gardenman]

A lot depends on the state of the food also. A cooked, more or less sterile product will cause fewer issues than an uncooked, potentially already bacteria laden product. I have no issues putting a cooked, deveined, frozen shrimp into a tank for grazing for a day. I've never seen an ammonia spike from doing so. The shrimp starts out cooked, deveined, and frozen, so active bacteria on it are very unlikely. If a similarly sized dead, intact fish was put into the tank for the other fish to graze on, the bacteria living inside that formerly alive fish would have a big head start on decomposition and you could crash a tank depending on the size of the tank and the dead fish.   

[Flumpweesel]

Dry food I've never had an issue with its pretty much all gone within an hour of feeding.

Veggies I've tried them a few times with limited success but left them in at least 12 hrs without problems. 

[Colu]

I usually leave vegetable in for 24hr with no problems the dried food and frozen don't last long enough to effect water quality if your routinely over feeding that will effect your water quality  

[nabokovfan87]

On 11/3/2022 at 4:23 PM, Aiden Carter said:

can we get some sort of list or something detailing how long certain foods can stay in the tank before heavily affecting water quality (for scavengers or grazers for example) 

As far as technical data, I just am not the one to provide that and be able to have some sort of scientific research for this one...

When it comes to my own experience with foods I do have a bit of history with food sitting and picky fish that straight up ignore the foods I feed them for a variety of reasons.

Algae wafers, spirulina wafers, etc. can sit in the tank for x amount of time based on what binders are in the wafer itself to keep it together.  If you have high flow, it'll break down a lot quicker as well.  Something like a hikari wafer, I generally don't pay too much attention to, but they can sit in the tank for about half a day up to around 12 hours before they turn to mush in some cases.  Extreme wafers break apart a bit sooner as well as the newer version of the sera wafers.  The pellets are a similar story.  I have had xtreme pellets float on the top of a tank for a solid 2 days and they didn't sink or break down.  The ones that sink, they can sit and hold there shape for a very, very long time.

But.... to your question about "how long until food in the tank affects water quality?"

I would argue it's pretty quick.  Food usually has phosphates and depending how much you're feeding and how often, just the amount of food that is left uneated after 15-30 minutes and will sit and float around the tank, you're encouraging phosphates which encourages algae.  Yes, that turns into ammonia, nitrite, and nitrates on some level and your plants do eat that waste, but I think all of us here have started a new tank using a pinch of flake food.

If you're having issues with the food itself being eaten, feed less.  If you're having issues with the fish rejecting food, give them time to want to eat it, feed less, and try other food to find out what they do like to eat.

Hopefully that helps.